British anti-invasion preparations of the Second World War entailed a large-scale division of military

Military history of the United Kingdom during World War II

Britain along with most of its dominions and Crown colonies, and British India, declared war on Nazi Germany in 1939. War with Japan began in 1941, after it attacked British colonies in Asia...

 and civilian mobilisation in response to the threat of invasion

Operation Sealion

Operation Sea Lion was Germany's plan to invade the United Kingdom during the Second World War, beginning in 1940. To have had any chance of success, however, the operation would have required air and naval supremacy over the English Channel...

 by German armed forces in 1940 and 1941

History of Germany during World War II

The history of Germany during World War II closely parallels that of Nazi Germany under Adolf Hitler. He came to power in Germany in 1933. From that point onward, Germany followed a policy of rearmament and confrontation with other countries...

. The British army

British Army

The British Army is the land warfare branch of Her Majesty's Armed Forces in the United Kingdom. It came into being with the unification of the Kingdom of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England...

 needed to recover from the defeat

Battle of Dunkirk

The Battle of Dunkirk was a battle in the Second World War between the Allies and Germany. A part of the Battle of France on the Western Front, the Battle of Dunkirk was the defence and evacuation of British and allied forces in Europe from 26 May–4 June 1940.After the Phoney War, the Battle of...

 of the British Expeditionary Force

British Expeditionary Force (World War II)

The British Expeditionary Force was the British force in Europe from 1939–1940 during the Second World War. Commanded by General Lord Gort, the BEF constituted one-tenth of the defending Allied force....

 in France, and 1.5 million men were enrolled as part-time soldiers in the Home Guard. The rapid construction of field fortifications transformed much of the United Kingdom, especially southern England

Southern England

Southern England, the South and the South of England are imprecise terms used to refer to the southern counties of England bordering the English Midlands. It has a number of different interpretations of its geographic extents. The South is considered by many to be a cultural region with a distinct...

, into a prepared battlefield.

The German invasion plan, Operation Sea Lion, was never taken beyond the preliminary assembly of forces. Today, little remains of Britain's anti-invasion preparations. Only reinforced concrete structures such as pillboxes are common.

Political and military background

On 1 September 1939, Germany invaded Poland; two days later, Britain and France declared war on Germany

Nazi Germany

Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

, launching the Second World War. Within three weeks, the Red Army

Red Army

The Workers' and Peasants' Red Army started out as the Soviet Union's revolutionary communist combat groups during the Russian Civil War of 1918-1922. It grew into the national army of the Soviet Union. By the 1930s the Red Army was among the largest armies in history.The "Red Army" name refers to...

 of the Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 invaded the eastern regions of Poland

Kresy

The Polish term Kresy refers to a land considered by Poles as historical eastern provinces of their country. Today, it makes western Ukraine, western Belarus, as well as eastern Lithuania, with such major cities, as Lviv, Vilnius, and Hrodna. This territory belonged to the Polish-Lithuanian...

 in fulfilment of the secret Molotov-Ribbentrop Pact

Molotov-Ribbentrop Pact

The Molotov–Ribbentrop Pact, named after the Soviet foreign minister Vyacheslav Molotov and the German foreign minister Joachim von Ribbentrop, was an agreement officially titled the Treaty of Non-Aggression between Germany and the Soviet Union and signed in Moscow in the late hours of 23 August 1939...

 with Germany. A British Expeditionary Force

British Expeditionary Force (World War II)

The British Expeditionary Force was the British force in Europe from 1939–1940 during the Second World War. Commanded by General Lord Gort, the BEF constituted one-tenth of the defending Allied force....

 (BEF) was sent to the Franco-Belgian border, but Britain and France did not take any direct action in support of the Poles. By 1 October, Poland had been completely overrun.

There was little fighting over the months that followed. In a period known as the Phoney War, French and British soldiers trained for war and constructed and manned defences on the eastern borders of France.

On 9 April 1940, Germany invaded Denmark and Norway

Operation Weserübung

Operation Weserübung was the code name for Germany's assault on Denmark and Norway during the Second World War and the opening operation of the Norwegian Campaign...

. This operation preempted the British plan to invade Norway for protective purposes. Denmark surrendered immediately, and after fierce fighting, Norway also fell. The invasion of Norway was a combined forces operation in which the German war machine projected its power across the sea; this German success would come to be seen by the British as a dire portent.

On 7 May and 8 May 1940, in the British House of Commons

British House of Commons

The House of Commons is the lower house of the Parliament of the United Kingdom, which also comprises the Sovereign and the House of Lords . Both Commons and Lords meet in the Palace of Westminster. The Commons is a democratically elected body, consisting of 650 members , who are known as Members...

, the Norway Debate

Norway Debate

The Norway Debate, sometimes called the Narvik Debate, was a famous debate in the British House of Commons that took place in May 1940. It led to the formation of a widely-based National Government led by Winston Churchill which was to govern Britain until the end of World War II in Europe...

 revealed intense dissatisfaction with and outright hostility toward the government of Prime Minister Neville Chamberlain

Neville Chamberlain

Arthur Neville Chamberlain FRS was a British Conservative politician who served as Prime Minister of the United Kingdom from May 1937 to May 1940. Chamberlain is best known for his appeasement foreign policy, and in particular for his signing of the Munich Agreement in 1938, conceding the...

. Two days later, with events moving swiftly, Chamberlain resigned and was succeeded by Winston Churchill

Winston Churchill

Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...

.

On 10 May 1940, Germany invaded France

Battle of France

In the Second World War, the Battle of France was the German invasion of France and the Low Countries, beginning on 10 May 1940, which ended the Phoney War. The battle consisted of two main operations. In the first, Fall Gelb , German armoured units pushed through the Ardennes, to cut off and...

. By that time, the BEF consisted of 10 infantry

Infantry

Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of combat arms, they are the backbone of armies...

 divisions in three corps

Corps

A corps is either a large formation, or an administrative grouping of troops within an armed force with a common function such as Artillery or Signals representing an arm of service...

, a tank

Tank

A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...

 brigade and a Royal Air Force

Royal Air Force

The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...

 detachment of around 500 aircraft. The BEF was pinned by a German diversionary attack through Belgium and then isolated by the main attack that came through the Ardennes

Ardennes

The Ardennes is a region of extensive forests, rolling hills and ridges formed within the Givetian Ardennes mountain range, primarily in Belgium and Luxembourg, but stretching into France , and geologically into the Eifel...

 forest. Well-equipped and highly mobile Panzer

Panzer

A Panzer is a German language word that, when used as a noun, means "tank". When it is used as an adjective, it means either tank or "armoured" .- Etymology :...

divisions of the Wehrmacht

Wehrmacht

The Wehrmacht – from , to defend and , the might/power) were the unified armed forces of Nazi Germany from 1935 to 1945. It consisted of the Heer , the Kriegsmarine and the Luftwaffe .-Origin and use of the term:...

overran the prepared defences. There was some fierce fighting, but most of the BEF withdrew to a small area around the French port of Dunkirk.

As things had gone badly for the allies in France, it became evident that some thought needed to be given to the possibility of having to resist an attempted invasion of Britain by German forces.

British Army

The evacuation of British and French forces (Operation Dynamo

Operation Dynamo

The Dunkirk evacuation, commonly known as the Miracle of Dunkirk, code-named Operation Dynamo by the British, was the evacuation of Allied soldiers from the beaches and harbour of Dunkirk, France, between 26 May and the early hours of 3 June 1940, because the British, French and Belgian troops were...

) began on 26 May with air cover provided by the RAF

Royal Air Force

The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...

 at heavy cost. Over the following ten days, 338,226 French and British soldiers were evacuated to Britain. Most of the personnel were brought back to Britain, but many of the army's vehicles, tanks, guns, ammunition and heavy equipment and the RAF's ground equipment and stores were left behind in France. Some soldiers returned even without their rifles. A further 215,000 were evacuated from ports south of the Channel in Operation Ariel

Operation Ariel

Operation Ariel was the name given to the World War II evacuation of Allied forces from ports in western France, from 15–25 June 1940, due to the military collapse in the Battle of France against Nazi Germany...

 during June.

In June 1940 the British Army

British Army

The British Army is the land warfare branch of Her Majesty's Armed Forces in the United Kingdom. It came into being with the unification of the Kingdom of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England...

 had 22 infantry divisions and one armoured division. The infantry divisions were, on average, at half strength, had only one-sixth of their normal artillery, and were almost totally lacking in transport. There was a critical shortage of ammunition such that none could be spared for practice. VII Corps was formed to control the Home Forces' general reserve, and included the 1st Armoured Division

British 1st Armoured Division

The 1st Armoured Division is an armoured division of the British Army. Originally formed in November 1937 as the Mobile Division, it saw extensive service during the Second World War, was disbanded afterward, was reconstituted in 1976, and remains in service today...

.

Home Guard

On 14 May 1940, Secretary of State for War Anthony Eden

Anthony Eden

Robert Anthony Eden, 1st Earl of Avon, KG, MC, PC was a British Conservative politician, who was Prime Minister from 1955 to 1957...

 announced the creation of the Local Defence Volunteers (LDV)—later to become known as the Home Guard. Far more men volunteered than the government expected and by the end of June, there were nearly 1.5 million volunteers. There were plenty of personnel for the defence of the country, but there were no uniforms (a simple armband had to suffice) and equipment was in critically short supply. At first, the Home Guard was armed with guns in private ownership, a knife or bayonet on a pole, Molotov cocktail

Molotov cocktail

The Molotov cocktail, also known as the petrol bomb, gasoline bomb, Molotov bomb, fire bottle, fire bomb, or simply Molotov, is a generic name used for a variety of improvised incendiary weapons...

s and improvised flamethrower

Flamethrower

A flamethrower is a mechanical device designed to project a long controllable stream of fire.Some flamethrowers project a stream of ignited flammable liquid; some project a long gas flame. Most military flamethrowers use liquids, but commercial flamethrowers tend to use high-pressure propane and...

s.

By July 1940 the situation had improved somewhat with uniforms, a modicum of training and the arrival of hundreds of thousands of rifles and millions of rounds of ammunition from the USA. New weapons were developed that could be produced cheaply without consuming materials that were needed to produce armaments for the regular units. An early example was the No. 76 Special Incendiary Grenade

No. 76 Special Incendiary Grenade

The No. 76 Special Incendiary Grenade also commonly known as the A.W. bomb or SIP Grenade was an incendiary grenade based on white phosphorus used during World War II....

 (a glass bottle filled with highly flammable material of which more than six million were made), and the No. 73 Grenade

No. 73 Grenade

The No. 73 grenade, also known as the Thermos or Woolworth bomb, was a British anti-tank grenade used during the Second World War. It got its nickname from the resemblance to a Thermos flask.-Development:...

 (an anti-tank grenade resembling a Thermos flask).

The sticky bomb

Sticky bomb

The Grenade, Hand, Anti-Tank No. 74, commonly known as the sticky bomb, was a British hand grenade designed and produced during the Second World War. The grenade was one of a number of anti-tank weapons developed for use by the British Army and Home Guard as an ad hoc solution to a lack of...

 was a glass flask filled with nitroglycerin and given an adhesive coating allowing it to be glued to a passing vehicle. In theory, it could be thrown, but in practice it would most likely need to be placed—thumped against the target with sufficient force to stick—requiring courage and good fortune to be used effectively. An order for one million sticky bombs was placed in June 1940, but various problems delayed their distribution in large numbers until early 1941, and it is likely that fewer than 250,000 were produced.

A measure of mobility was provided by bicycles, motorcycles, private vehicles and horses. A small number of units were equipped with armoured cars, some of which were of standard design, but many were improvised locally from commercially available vehicles by the attachment of steel plates.

Later in 1941, more sophisticated weapons were made available such as the Blacker Bombard

Blacker Bombard

The Blacker Bombard, also known as the 29mm Spigot Mortar, was an infantry anti-tank weapon devised by Lieutenant-Colonel Stewart Blacker in the early years of the Second World War.-Development:...

 anti-tank weapon, the Northover Projector

Northover projector

The Projector, 2.5 inch—more commonly known as the Northover Projector—was an ad hoc anti-tank weapon used by the British Army and Home Guard during the Second World War...

 (a black-powder mortar), and the Smith Gun

Smith Gun

The Smith Gun was an ad hoc anti-tank artillery piece used by the British Army and Home Guard during the Second World War. With a German invasion of Great Britain seeming likely after the defeat in the Battle of France, most available weaponry was diverted to the regular British Army, leaving the...

 (a small artillery gun that could be towed by a private motorcar).

Royal Air Force

In mid-1940, the principal concern of the Royal Air Force

Royal Air Force

The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...

, together with elements of the Fleet Air Arm

Fleet Air Arm

The Fleet Air Arm is the branch of the British Royal Navy responsible for the operation of naval aircraft. The Fleet Air Arm currently operates the AgustaWestland Merlin, Westland Sea King and Westland Lynx helicopters...

, was to contest the control of British airspace with the German Luftwaffe

Luftwaffe

Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....

. For the Germans, achieving at least local air superiority was an essential prerequisite to any invasion.

If the German air force had prevailed and attempted a landing, a much-reduced Royal Air Force would have been obliged to operate from airfields well away from the south east of England. Any airfield that was in danger of being captured would have been made inoperable and there were plans to remove all portable equipment from vulnerable radar

Radar

Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

 bases and completely destroy anything that could not be moved. Whatever was left of the RAF would have been committed to intercepting the invasion fleet in concert with the Royal Navy—to fly in the presence of an enemy that enjoys air superiority is very dangerous. However, the RAF would have kept several advantages, such as being able to operate largely over friendly territory, as well as having the ability to fly for longer as, until the Germans were able to operate from airfields in England, Luftwaffe pilots would still have to fly significant distances to reach their operational area.

A contingency plan called Operation Banquet

Operation Banquet

Operation Banquet was a British plan to use every available aircraft in a last ditch effort to repel an expected German invasion in 1940 or 1941. During the Second World War, in May 1940, the Air Ministry realised that beyond the normal reserves of the Royal Air Force , it may be necessary to throw...

 required all available aircraft to be committed to the defence. In the event of invasion almost anything that was not a fighter would be converted to a bomber – student pilots, some in the very earliest stages of training, would use around 350 Tiger Moth

De Havilland Tiger Moth

The de Havilland DH 82 Tiger Moth is a 1930s biplane designed by Geoffrey de Havilland and was operated by the Royal Air Force and others as a primary trainer. The Tiger Moth remained in service with the RAF until replaced by the de Havilland Chipmunk in 1952, when many of the surplus aircraft...

 and Magister

Miles Magister

-See also:-References:NotesBibliography* Amos, Peter. Miles Aircraft = The early years. Tonbridge: Air-Britain, 2009. ISBN 978 0 85130 410 6...

 trainers to drop 20 lb (9.1 kg) bombs from rudimentary bomb racks.

Shortly before the outbreak of the Second World War the Chain Home

Chain Home

Chain Home was the codename for the ring of coastal Early Warning radar stations built by the British before and during the Second World War. The system otherwise known as AMES Type 1 consisted of radar fixed on top of a radio tower mast, called a 'station' to provide long-range detection of...

 radar system began to be installed in the south of England, with three radar stations being operational by 1937. Although the German High Command suspected that the British may have been developing these systems, Zeppelin

Zeppelin

A Zeppelin is a type of rigid airship pioneered by the German Count Ferdinand von Zeppelin in the early 20th century. It was based on designs he had outlined in 1874 and detailed in 1893. His plans were reviewed by committee in 1894 and patented in the United States on 14 March 1899...

 test flights had proved inconclusive. As a result the expanding Chain Home radar system, and aircraft-based radar first fielded in 1940, became a vital piece of Britain's defensive capabilities during the Battle of Britain

Battle of Britain

The Battle of Britain is the name given to the World War II air campaign waged by the German Air Force against the United Kingdom during the summer and autumn of 1940...

.

Royal Navy

The British Home Fleet

British Home Fleet

The Home Fleet was a fleet of the Royal Navy which operated in the United Kingdom's territorial waters from 1902 with intervals until 1967.-Pre–First World War:...

 was a force that dwarfed anything the Kriegsmarine

Kriegsmarine

The Kriegsmarine was the name of the German Navy during the Nazi regime . It superseded the Kaiserliche Marine of World War I and the post-war Reichsmarine. The Kriegsmarine was one of three official branches of the Wehrmacht, the unified armed forces of Nazi Germany.The Kriegsmarine grew rapidly...

 could put to sea. On 1 July, one cruiser and 23 destroyers were committed to escort duties in the Western Approaches

Western Approaches

The Western Approaches is a rectangular area of the Atlantic ocean lying on the western coast of Great Britain. The rectangle is higher than it is wide, the north and south boundaries defined by the north and south ends of the British Isles, the eastern boundary lying on the western coast, and the...

, plus 12 destroyers and one cruiser on the Tyne and the aircraft carrier

Aircraft carrier

An aircraft carrier is a warship designed with a primary mission of deploying and recovering aircraft, acting as a seagoing airbase. Aircraft carriers thus allow a naval force to project air power worldwide without having to depend on local bases for staging aircraft operations...

 Argus

HMS Argus (I49)

HMS Argus was a British aircraft carrier that served in the Royal Navy from 1918–1944. She was converted from an ocean liner under construction when the First World War began, and became the world's first example of what is now the standard pattern of aircraft carrier, with a full-length flight...

. More immediately available were ten destroyers at the south coast ports of Dover

Dover

Dover is a town and major ferry port in the home county of Kent, in South East England. It faces France across the narrowest part of the English Channel, and lies south-east of Canterbury; east of Kent's administrative capital Maidstone; and north-east along the coastline from Dungeness and Hastings...

 and Portsmouth

Portsmouth

Portsmouth is the second largest city in the ceremonial county of Hampshire on the south coast of England. Portsmouth is notable for being the United Kingdom's only island city; it is located mainly on Portsea Island...

, a cruiser and three destroyers at Sheerness

Sheerness

Sheerness is a town located beside the mouth of the River Medway on the northwest corner of the Isle of Sheppey in north Kent, England. With a population of 12,000 it is the largest town on the island....

 on the River Thames

River Thames

The River Thames flows through southern England. It is the longest river entirely in England and the second longest in the United Kingdom. While it is best known because its lower reaches flow through central London, the river flows alongside several other towns and cities, including Oxford,...

, three cruisers and seven destroyers at the Humber

Humber

The Humber is a large tidal estuary on the east coast of Northern England. It is formed at Trent Falls, Faxfleet, by the confluence of the tidal River Ouse and the tidal River Trent. From here to the North Sea, it forms part of the boundary between the East Riding of Yorkshire on the north bank...

, 9 destroyers at Harwich

Harwich

Harwich is a town in Essex, England and one of the Haven ports, located on the coast with the North Sea to the east. It is in the Tendring district. Nearby places include Felixstowe to the northeast, Ipswich to the northwest, Colchester to the southwest and Clacton-on-Sea to the south...

, and two cruisers at Rosyth

Rosyth

Rosyth is a town located on the Firth of Forth, three miles south of the centre of Dunfermline. According to an estimate taken in 2008, the town has a population of 12,790....

. The rest of the Home Fleet—five battleships, three cruisers and nine destroyers—was based far to the north at Scapa Flow

Scapa Flow

right|thumb|Scapa Flow viewed from its eastern endScapa Flow is a body of water in the Orkney Islands, Scotland, United Kingdom, sheltered by the islands of Mainland, Graemsay, Burray, South Ronaldsay and Hoy. It is about...

. There were, in addition, many corvette

Corvette

A corvette is a small, maneuverable, lightly armed warship, originally smaller than a frigate and larger than a coastal patrol craft or fast attack craft , although many recent designs resemble frigates in size and role...

s, minesweepers

Minesweeper (ship)

A minesweeper is a small naval warship designed to counter the threat posed by naval mines. Minesweepers generally detect then neutralize mines in advance of other naval operations.-History:...

, and other small vessels. By the end of July, a dozen additional destroyers were transferred from escort duties to the defence of the homeland, and more would join the Home Fleet shortly after. At the end of August, the battleship HMS Rodney was sent south to Rosyth

Rosyth

Rosyth is a town located on the Firth of Forth, three miles south of the centre of Dunfermline. According to an estimate taken in 2008, the town has a population of 12,790....

 for anti-invasion duties. She was joined on 13 September by her sister ship HMS Nelson, the battlecruiser HMS Hood

HMS Hood (51)

HMS Hood was the last battlecruiser built for the Royal Navy. One of four s ordered in mid-1916, her design—although drastically revised after the Battle of Jutland and improved while she was under construction—still had serious limitations. For this reason she was the only ship of her class to be...

, three anti-aircraft cruisers and a destroyer flotilla. Destroyers made regular night-time sweeps of the Channel and on 8 September, two cruisers and 10 destroyers swept the French coast and bombarded Boulogne harbour. On 25 September, a sortie intending to send fire ship

Fire ship

A fire ship, used in the days of wooden rowed or sailing ships, was a ship filled with combustibles, deliberately set on fire and steered into an enemy fleet, in order to destroy ships, or to create panic and make the enemy break formation. Ships used as fire ships were usually old and worn out or...

s into French ports to destroy invasion barges, codenamed Operation Lucid

Operation Lucid

Operation Lucid was a British plan to use fire ships to attack invasion barges that were gathering in ports on the northern coast of France in preparation for a German invasion of Britain in 1940...

, was abandoned when both the old tankers that were to be used had engine failure.

Field fortifications

The British engaged upon an extensive programme of field fortification.

On 27 May 1940 a Home Defence Executive was formed under General Sir Edmund Ironside

Edmund Ironside, 1st Baron Ironside

Field Marshal William Edmund Ironside, 1st Baron Ironside GCB, CMG, CBE, DSO, was a British Army officer who served as Chief of the Imperial General Staff during the first year of the Second World War....

, Commander-in-Chief Home Forces, to organise the defence of Britain. At first defence arrangements were largely static and focused on the coastline (the coastal crust) and, in a classic example of defence in depth

Defence in depth

Defence in depth is a military strategy; it seeks to delay rather than prevent the advance of an attacker, buying time and causing additional casualties by yielding space...

, on a series of inland anti-tank 'stop' lines. The stop lines were designated Command, Corp and Divisional according to their status. The longest and most heavily fortified was the General Headquarters anti-tank line, GHQ Line

GHQ Line

The GHQ Line was a defence line built in the United Kingdom during World War II to contain an expected German invasion.The British Army had abandoned most of its equipment in France after the Dunkirk evacuation...

, which ran across southern England, wrapped around London and then ran north to Yorkshire. It was intended to protect the capital and the industrial heartland of England. Another major line was the Taunton Stop Line

Taunton Stop Line

The Taunton Stop Line was a World War II defensive line in south west England. It was designed "to stop an enemy's advance from the west and in particular a rapid advance supported by armoured fighting vehicles which may have broken through the forward defences."The Taunton Stop Line was one of...

, which defended against an advance from England's south-west peninsula. London and other major cities were ringed with inner and outer stop lines. Some 50 stop lines were constructed, some of the less important lines were just demolition belt

Demolition belt

In military terminology, a demolition belt is a selected land area sown with explosive charges, mines, and other available obstacles to deny use of the land to enemy operations, and as a protection to friendly troops.There are two types of demolition belt:...

s and not all lines were completed.

Military thinking shifted rapidly. Given the lack of equipment and properly trained men, Ironside had had little choice but to adopt a strategy of static warfare, but it was soon perceived that this would not be sufficient. Ironside has been criticised for having a siege mentality, but some consider this unfair, as he is believed to have understood the limits of the stop lines and never expected them to hold out indefinitely.

However, Prime Minister Churchill was not satisfied with Ironside's progress, especially with regard to the creation of a mobile reserve. Anthony Eden

Anthony Eden

Robert Anthony Eden, 1st Earl of Avon, KG, MC, PC was a British Conservative politician, who was Prime Minister from 1955 to 1957...

, the Secretary of State for War, suggested that Ironside should be replaced by General Brooke

Alan Brooke, 1st Viscount Alanbrooke

Field Marshal The Rt. Hon. Alan Francis Brooke, 1st Viscount Alanbrooke, KG, GCB, OM, GCVO, DSO & Bar , was a senior commander in the British Army. He was the Chief of the Imperial General Staff during the Second World War, and was promoted to Field Marshal in 1944...

 (later Viscount Alanbrooke). On 17 July 1940 Churchill spent an afternoon with Brooke and was soon convinced that they were in close agreement as to how best to defend the nation. On 19 July Brooke replaced Ironside.

Brooke's appointment coincided with more trained men and better equipment becoming available. Under Brooke, new strategies and tactics were devised. More concentration was placed on defending the coastal crust, while inland a hedgehog defence

Hedgehog defence

In warfare, the hedgehog defence is a military tactic for defending against a mobile armoured attack, or blitzkrieg. The defenders deploy in depth in heavily fortified positions suitable for all-around defence. The attackers can penetrate between these "hedgehogs", but each position continues to...

 strategy of defended localities and anti-tank islands was established, each having all-round defence. Many of these anti-tank islands were established along the already constructed stop lines, where existing defences could be integrated into the new strategy and, especially, at towns and villages where there was a Home Guard to provide personnel.

Coastal crust

Any German invasion of Britain would have to involve the landing of troops and equipment somewhere on the coast, and the most vulnerable areas were the south and east coasts of England. Here, Emergency Coastal Batteries were constructed to protect ports and likely landing places. They were fitted with whatever guns were available, which mainly came from naval vessels scrapped since the end of the First World War. These included 6 inch (152 mm), 5.5 inch (140 mm), 4.7 inch (120 mm) and 4 inch (102 mm) guns. These had little ammunition, sometimes as few as ten rounds apiece. At Dover, two 14 inch (356 mm) guns known as Winnie and Pooh were employed. There were also a small number of land based torpedo launching sites.

Beaches were blocked with entanglements of barbed wire, usually in the form of three coils of concertina wire

Concertina wire

Concertina wire or Dannert Wire is a type of barbed wire or razor wire that is formed in large coils which can be expanded like a concertina. In conjunction with plain barbed wire and steel pickets, it is used to form military wire obstacles....

 fixed by metal posts, or a simple fence of straight wires supported on waist-high posts. The wire would also demarcate extensive minefields, with both anti-tank and anti-personnel mines on and behind the beaches. On many of the more remote beaches this combination of wire and mines represented the full extent of the passive defences.

Portions of the Romney Marsh

Romney Marsh

Romney Marsh is a sparsely populated wetland area in the counties of Kent and East Sussex in the south-east of England. It covers about 100 mi ² .-Quotations:*“As Egypt was the gift of the Nile, this level tract .....

, which was the planned invasion site of Operation Sea Lion, were flooded and there were plans to flood more of the Marsh if the invasion were to materialise.

Piers, ideal for landing of troops, and situated in large numbers along the south coast of England, were disassembled, blocked or otherwise destroyed. Many piers were not repaired until the late 1940s or early 1950s.

Where a barrier to tanks was required, Admiralty scaffolding

Admiralty scaffolding

Admiralty scaffolding, also known as Obstacle Z.1 or sometimes simply given as beach scaffolding or anti-tank scaffolding, was a British design of anti-tank and anti-boat obstacle made of tubular steel. It was widely deployed on beaches of southern England, eastern England and the south western...

 (also known as beach scaffolding or obstacle Z.1) was constructed. Essentially, this was a fence of scaffolding tubes 9 feet (2.7 m) high and was placed at low water so that tanks could not get a good run at it. Admiralty scaffolding was deployed along hundreds of miles of vulnerable beaches.

An even more robust barrier to tanks was provided by long lines of anti-tank cubes. The cubes were made of reinforced concrete 5 feet (1.5 m) to a side. Thousands were cast in situ in rows sometimes two or three deep.

The beaches themselves were overlooked by pillboxes of various types (see British hardened field defences of the Second World War

British hardened field defences of World War II

British hardened field defences of World War II were small fortified structures constructed as a part of British anti-invasion preparations. They were popularly known as pillboxes by reference to their shape.-Design and development:...

). These were sometimes placed low down to get maximum advantage from enfilading fire

Enfilade and defilade

Enfilade and defilade are concepts in military tactics used to describe a military formation's exposure to enemy fire. A formation or position is "in enfilade" if weapons fire can be directed along its longest axis. A unit or position is "in defilade" if it uses natural or artificial obstacles to...

 whereas others were placed high up making them much harder to capture. Searchlights were installed at the coast to illuminate the sea surface and the beaches for artillery fire.

Many small islands and peninsulas were fortified to protect inlets and other strategic targets. In the Firth of Forth

Firth of Forth

The Firth of Forth is the estuary or firth of Scotland's River Forth, where it flows into the North Sea, between Fife to the north, and West Lothian, the City of Edinburgh and East Lothian to the south...

 in east central Scotland, Inchgarvie Island

Inchgarvie

Inchgarvie is a small, uninhabited island in the Firth of Forth. Its name comes from Innis Garbhach which is Scottish Gaelic for "rough island"...

 was heavily fortified with several gun emplacements, which can still be seen. This provided invaluable defence from seaborne attacks on the Forth Bridge and Rosyth Dockyard

Rosyth Dockyard

Rosyth Dockyard is a large naval dockyard on the Firth of Forth at Rosyth, Fife, Scotland, owned by Babcock Marine, which primarily undertakes refitting of Royal Navy surface vessels.-History:...

, approximately a mile upstream from the bridge. Further out to sea, Inchmickery Island

Inchmickery

Inchmickery is a small island in the Firth of Forth in Scotland. It is about a mile north of Edinburgh.Its name comes from the Scottish Gaelic, Innis nam Bhiocaire, meaning Isle of the Vicar, implying that there may have been an old ecclesiastical or Culdee settlement here, as in nearby Inchcolm...

, 1.6 miles (2.6 km) north of Edinburgh, was similarly fortified. The remnants of gun emplacements on the coast to the north, in North Queensferry

North Queensferry

North Queensferry is a village in Fife, Scotland, on the Firth of Forth, between the Forth Bridge and the Forth Road Bridge, and from Edinburgh. According to the 2008 population estimate, the village has a population of 1,150. It is the southernmost settlement in Fife.The Scottish Gaelic name...

, and south, in Dalmeny

Dalmeny

Dalmeny is a suburban village and civil parish in Edinburgh, Scotland. It is located on the south side of the Firth of Forth, east-southeast of South Queensferry and west-northwest of central Edinburgh; it falls under the local governance of the City of Edinburgh Council.The name Dalmeny is...

, of Inchmickery Island also remain.

Lines and islands

The primary purpose of the stop lines and the anti-tank islands that followed was to hold up the enemy, slowing progress and restricting the route of an attack. The need to prevent tanks from breaking through was of key importance. Consequently, the defences generally ran along pre-existing barriers to tanks such as rivers and canals; railway embankments and cuttings; thick woods; and other natural obstacles. Where possible, usually well-drained land was allowed to flood making the ground too soft to support even tracked vehicles.

Thousands of miles of anti-tank ditches were dug, usually by mechanical excavators, but occasionally by hand. They were typically 18 feet (5.5 m) wide and 11 feet (3.4 m) deep and could be either trapezoidal or triangular in section with the defended side being especially steep and revetted

Revetment

Revetments, or revêtements , have a variety of meanings in architecture, engineering and art history. In stream restoration, river engineering or coastal management, they are sloping structures placed on banks or cliffs in such a way as to absorb the energy of incoming water...

 with whatever material was available.

Elsewhere, anti-tank barriers were made of massive reinforced concrete obstacles, either cubic, pyramidal or cylindrical. The cubes generally came in two sizes: 5 feet (1.5 m) or 3.5 feet (1.1 m) high. In a few places, anti-tank walls were constructed—essentially continuously abutted cubes.

Large cylinders were made from a section of sewer pipe 3 to 4 ft (91.4 to 121.9 cm) in diameter filled with concrete typically to a height of 4 to 5 ft (1.2 to 1.5 m), frequently with a dome at the top. Smaller cylinders cast from concrete are also frequently found.

Pimples, popularly known as Dragon's teeth

Dragon's teeth (fortification)

Dragon's teeth are square-pyramidal fortifications of reinforced concrete first used during the Second World War to impede the movement of tanks and mechanised infantry...

, were pyramid shaped concrete blocks designed specifically to counter tanks which, attempting to pass them, would climb up exposing vulnerable parts of the vehicle and possibly slip down with the tracks between the points. They ranged in size somewhat, but were typically 2 feet (61 cm) high and about 3 feet (91.4 cm) square at the base. There was also a conical form.

Cubes, cylinders and pimples were deployed in long rows, often several rows deep, to form anti-tank barriers at beaches and inland. They were also used in smaller numbers to block roads. They frequently sported loops at the top for the attachment of barbed wire. There was also a tetrahedral or caltrop

Caltrop

A caltrop is an antipersonnel weapon made up of two or more sharp nails or spines arranged in such a manner that one of them always points upward from a stable base...

-shaped obstacle, although it seems these were rare.

Where natural anti-tank barriers needed only to be augmented, concrete or wooden posts sufficed.

Roads offered the enemy fast routes to their objectives and consequently they were blocked at strategic points. Many of the road-blocks formed by Ironside were semi-permanent. In many cases, Brooke had these removed altogether, as experience had shown they could be as much of an impediment to friends as to foes. Brooke favoured removable blocks.

The simplest of the removable roadblocks consisted of concrete cylinders of various sizes but typically about 3 foot (0.9144 m) high and 2 feet (61 cm) in diameter; these could be manhandled into position as required. However, these would be insufficient to stop armoured vehicles. One common type of removable anti-tank roadblock comprised massive concrete posts permanently installed at the roadside; these posts had holes and/or slots to accept horizontal railway lines or rolled steel joists (RSJs)

I-beam

-beams, also known as H-beams, W-beams , rolled steel joist , or double-T are beams with an - or H-shaped cross-section. The horizontal elements of the "" are flanges, while the vertical element is the web...

. Similar blocks were placed across railway tracks because tanks can move along tracks almost as easily as they can along roads. These blocks would be placed strategically where it was difficult for a vehicle to go around—anti-tank obstacles and mines being positioned as required—and they could be opened or closed within a matter of minutes.

There were two types of socket roadblocks. The first comprised vertical lengths of railway line placed in sockets in the road, was known as hedgehog. The second type comprised railway lines or RSJs bent or welded at around a 60° angle, known as hairpins. In both cases, prepared sockets about 6 inches (152.4 mm) square were placed in the road, closed by covers when not in use, allowing traffic to pass normally.

Another removable roadblocking system used mines. The extant remains of such systems superficially resemble those of hedgehog or hairpin, but the pits are shallow: just deep enough to take an anti-tank mine. When not in use, the sockets were filled with a wooden plug allowing traffic to pass normally.

Bridges and other key points were prepared for demolition at short notice by preparing chambers filled with explosives. A Depth Charge Crater was a site in a road (usually at a junction) prepared with buried explosives that could be detonated to instantly form a deep crater as an anti-tank obstacle. The Canadian pipe mine

Canadian pipe mine

The Canadian pipe mine, also known as the McNaughton tube, was a type of landmine deployed in Britain during the invasion crisis of 1940-1941...

 (later known as the McNaughton Tube after General Andrew McNaughton

Andrew McNaughton

General Andrew George Latta McNaughton, CH, CB, CMG, DSO, CD, PC was a Canadian army officer, politician and diplomat.- Early life :...

) was a horizontally bored

Directional drilling

Directional drilling is the practice of drilling non-vertical wells. It can be broken down into three main groups: Oilfield Directional Drilling, Utility Installation Directional Drilling Directional drilling (or slant drilling) is the practice of drilling non-vertical wells. It can be broken down...

 pipe packed with explosives – once in place this could be used to instantly ruin a road or runway. Prepared demolitions had the advantage of being undetectable from the air—the enemy could not take any precautions against them, or plot a route of attack around them.

Crossing points in the defence network – bridges, tunnels and other weak spots – were called nodes or points of resistance. These were fortified with removable road blocks, barbed wire entanglements, and land mines. These passive defences were overlooked by trench works, gun and mortar emplacements, and pillboxes. In places entire villages were fortified using barriers of scaffolding

Admiralty scaffolding

Admiralty scaffolding, also known as Obstacle Z.1 or sometimes simply given as beach scaffolding or anti-tank scaffolding, was a British design of anti-tank and anti-boat obstacle made of tubular steel. It was widely deployed on beaches of southern England, eastern England and the south western...

, sandbag

Sandbag

A sandbag is a sack made of hessian/burlap, polypropylene or other materials that is filled with sand or soil and used for such purposes as flood control, military fortification, shielding glass windows in war zones and ballast....

ged positions and loopholes in existing buildings.

Nodes were designated 'A', 'B' or 'C' depending upon how long they were expected to hold out. Home Guard troops were largely responsible for the defence of nodal points and other centres of resistance such as towns and defended villages. Category 'A' nodal points and anti-tank islands usually had a garrison of regular troops.

The rate of construction was frenetic: by the end of September 1940, 18,000 pillboxes and countless other preparations had been completed.

Airfields and open areas

Open areas were considered vulnerable to invasion from the air: a landing by paratroops, glider-borne troops or powered aircraft which could land and take off again. Open areas with a straight length of 500 yards (457.2 m) or more within five miles (8 km) of the coast or an airfield were considered vulnerable. These were blocked by trenches or, more usually, by wooden or concrete obstacles, as well as old cars.

Securing an airstrip would be an important objective for the invader. Airfields, considered extremely vulnerable, were protected by trench works and pillboxes which face inwards towards the runway, rather than outwards. Many of these fortifications were specified by the Air Ministry

Air Ministry

The Air Ministry was a department of the British Government with the responsibility of managing the affairs of the Royal Air Force, that existed from 1918 to 1964...

 and defensive designs were unique to airfields—these would not be expected to face heavy weapons so the degree of protection was less and there was more emphasis on all-round visibility and sweeping fields of fire. It was difficult to defend large open areas without creating impediments to the movement of friendly aircraft. Solutions to this problem included the pop-up Picket Hamilton fort—a light pillbox that could be lowered to ground level when the airfield was in use.

Another innovation was a mobile pillbox that could be driven out onto the airfield, this was known as the Bison and consisted of a lorry with a concrete armoured cabin and a small concrete pillbox on the flat bed.
Constructed in Canada, a 'runway plough', assembled in Scotland, survives at Eglinton Country Park

Eglinton Country Park

Eglinton Country Park is located in the grounds of the old Eglinton Castle estate, Kilwinning, North Ayrshire, Scotland . Eglinton Park is situated in the parish of Kilwinning, part of the former district of Cunninghame, and covers an area of 400 hectares...

. It was purchased by the army in World War II to rip up aerodrome runways and railway lines if an invasion took place as means of causing disruption making it useless for the would-have-been occupiers on the act of resistance. It was used at the old Eglinton Estate, which had been commandeered by the army, to provide its army operators with the necessary experience. It was hauled by a powerful Foden Trucks

Foden Trucks

Foden Trucks was a British truck and bus manufacturing company which has its origins in Sandbach, Cheshire in 1856. PACCAR acquired the company in 1980, and ceased to use the marque name in 2006.-History:...

 tractor, possibly via a pulley and cable system.

Hardened field defences

The field fortifications constructed throughout Britain included large numbers of hardened field defences: mostly in the form of pillboxes.

In May 1940, the Directorate of Fortifications and Works (FW3) was set up at the War Office. Its purpose was to provide a number of basic pillbox designs which could be constructed by soldiers and local labour at appropriate defensive locations. In the following June and July FW3 issued 6 basic designs for rifle and light machine gun pillboxes, designated Type 22 to Type 27. In addition, there were designs for gun emplacements suitable for either the Ordnance QF 2 pounder

Ordnance QF 2 pounder

The Ordnance QF 2-pounder was a British anti-tank and vehicle-mounted gun, employed in the Second World War. It was actively used in the Battle of France, and during the North Africa campaign...

 or the Hotchkiss 6 pounder gun

QF 6 pounder 6 cwt Hotchkiss

The Ordnance QF 6 pounder 6 cwt Hotchkiss Mk 1 and Mk 2 was a shortened version of the original QF 6 pounder Hotchkiss, and was developed specifically for use in the sponsons of the later Marks of British tanks in World War I, from Mark IV onwards.-History:...

 (designated Type 28) and a design for a hardened medium machine gun emplacement.

There were also designs for pillbox-like structures for various purposes including light anti-aircraft positions, observation posts and searchlight positions to illuminate the shoreline.

A small number of pillboxes had been constructed in the First World War and where possible these were integrated into the defence plans. Some pillboxes may predate the publication of the FW3 designs, but in any case some local commanders introduced modifications to the standard FW3 designs or introduced designs of their own. These non-standard design pillboxes may be produced in some numbers or completely ad hoc designs suited to local conditions. Other designs were produced as commercial ventures.

About 28,000 pillboxes and other hardened field fortifications were constructed in the United Kingdom of which about 6,500 still survive.

Other defensive measures

Other basic defensive measures included the removal of signposts, milestones (some had the carved details obscured with cement) and railway station signs

Running in board

A running in board is a large sign showing the name of the railway station on which it is found. The signs are intended to help passengers discover their location when on a train entering the station, possibly while still moving at speed....

 making it more likely that an enemy would become confused. Petrol pumps were removed from service stations near the coast and there were careful preparations for the destruction of those that were left. Detailed plans were made for the destruction of anything that might prove useful to the invader such as port facilities, key roads and rolling stock

Rolling stock

Rolling stock comprises all the vehicles that move on a railway. It usually includes both powered and unpowered vehicles, for example locomotives, railroad cars, coaches and wagons...

. In certain areas non-essential citizens were evacuated

Evacuations of civilians in Britain during World War II

Evacuation of civilians in Britain during the Second World War was designed to save the population of urban or military areas in the United Kingdom from aerial bombing of cities and military targets such as docks. Civilians, particularly children, were moved to areas thought to be less at risk....

. In the county of Kent

Kent

Kent is a county in southeast England, and is one of the home counties. It borders East Sussex, Surrey and Greater London and has a defined boundary with Essex in the middle of the Thames Estuary. The ceremonial county boundaries of Kent include the shire county of Kent and the unitary borough of...

, 40% of the population was relocated; in East Anglia

East Anglia

East Anglia is a traditional name for a region of eastern England, named after an ancient Anglo-Saxon kingdom, the Kingdom of the East Angles. The Angles took their name from their homeland Angeln, in northern Germany. East Anglia initially consisted of Norfolk and Suffolk, but upon the marriage of...

, the figure was 50%.

Perhaps most importantly, the population was told what was expected from them. In June 1940, the Ministry of Information published If the Invader Comes, what to do—and how to do it. It began:
The first instruction given quite emphatically is that, unless ordered to evacuate, "THE ORDER IS 'STAY PUT' " [capitalisation as in original]. The roads were not to be blocked by refugees. Further warnings were given not to believe rumours and not to spread them, to be distrustful of orders that might be faked and even to check that an officer giving orders really is British. Further: keep calm and report anything suspicious quickly and accurately; deny useful things to the enemy such as food, fuel, maps or transport; be ready to block roads—when ordered to do so—"by felling trees, wiring them together or blocking the roads with cars"; to organise resistance at shops and factories; and, finally:
On 13 June 1940 the ringing of church bells was banned; henceforth they would only be rung by the military or the police to warn that an invasion—generally meaning by parachutists—was in progress.
In 1941, in towns and villages invasion committees were formed to cooperate with the military and plan for the worst should their communities be isolated or occupied. The members of committees typically included representatives of the local council, the Air Raid Precautions

Air Raid Precautions

Air Raid Precautions was an organisation in the United Kingdom set up as an aid in the prelude to the Second World War dedicated to the protection of civilians from the danger of air-raids. It was created in 1924 as a response to the fears about the growing threat from the development of bomber...

 service, the fire service, the police, the Women’s Voluntary Service

WRVS

The WRVS is a voluntary organisation concerned with helping people in need throughout England, Scotland and Wales....

 and the Home Guard, as well as officers for medicine, sanitation and food. Plans of these committees were kept in secret War Books although few remain. Detailed inventories of anything useful were kept: vehicles, animals and basic tools, and lists were made of contact details for key personnel. Plans were made for a wide range of emergencies, including improvised mortuaries and places to bury the dead. Instructions to the Invasion Committees stated: "...every citizen will regard it as his duty to hinder and frustrate the enemy and help our own forces by every means that ingenuity can devise and common sense suggest."

It is clear that more than merely passive resistance was expected—or at least hoped for—from the population. Churchill considered the formation of a Home Guard Reserve, given only an armband and basic training on the use of simple weapons such as Molotov cocktails. The reserve would only have been expected to report for duty in an invasion. Later, Churchill wrote how he envisaged the use of the sticky bomb

Sticky bomb

The Grenade, Hand, Anti-Tank No. 74, commonly known as the sticky bomb, was a British hand grenade designed and produced during the Second World War. The grenade was one of a number of anti-tank weapons developed for use by the British Army and Home Guard as an ad hoc solution to a lack of...

: "We had the picture in mind that devoted soldiers or civilians would run close up to the tank and even thrust the bomb upon it, though its explosion cost them their lives [Italics added for emphasis]." He also later recorded how he intended to use the slogan "You can always take one with you."

When the UK went to war on 3 September 1939, the strength of the Metropolitan Police

Metropolitan Police Service

The Metropolitan Police Service is the territorial police force responsible for Greater London, excluding the "square mile" of the City of London which is the responsibility of the City of London Police...

 stood at 18,428, which was 900 officers short of full strength. Due to the threat of invasion three reserve groups were mobilised, the first consisted of 2,737 police pensioners who were re-engaged, a second reserve of 5,380 Special Constables

Metropolitan Special Constabulary

The Metropolitan Special Constabulary is the part-time volunteer police force of Greater London's Metropolitan Police Service. Created nearly 180 years ago under the Special Constables Act of 1831, it currently consists of nearly 5,000 volunteer police officers...

 serving on a temporary full time basis for the duration of the war, and 18,868 War Reserve Constables employed on the same basis as the Special Constables. On the same day as the Battle of Dunkirk

Battle of Dunkirk

The Battle of Dunkirk was a battle in the Second World War between the Allies and Germany. A part of the Battle of France on the Western Front, the Battle of Dunkirk was the defence and evacuation of British and allied forces in Europe from 26 May–4 June 1940.After the Phoney War, the Battle of...

, Scotland Yard

Scotland Yard

Scotland Yard is a metonym for the headquarters of the Metropolitan Police Service of London, UK. It derives from the location of the original Metropolitan Police headquarters at 4 Whitehall Place, which had a rear entrance on a street called Great Scotland Yard. The Scotland Yard entrance became...

 issued a memorandum detailing the police use of firearms

Police use of firearms in the United Kingdom

In the United Kingdom, the majority of police officers do not carry firearms, except in special circumstances. This originates from the formation of the Metropolitan Police Service in the 19th century, when police were not armed, partly to counter public fears and objections concerning armed...

 in wartime. This detailed the planned training for all officers in the use of pistols and revolvers, as it was decided that even though the police was non-combatant, they would provide armed guarding at sites deemed a risk from enemy sabotage, and would assist the British Armed Forces in the event of an invasion. Because of the possibility of the police assisting the armed forces, firearms and ammunition

Ammunition

Ammunition is a generic term derived from the French language la munition which embraced all material used for war , but which in time came to refer specifically to gunpowder and artillery. The collective term for all types of ammunition is munitions...

 supplied to divisions

Police division

A division was the usual term for the largest territorial subdivision of most British police forces. In major reforms of police organisation in the 1990s divisions of many forces were restructured and retitled Basic Command Units , although some forces continue to refer to them as divisions.The...

 were increased. On 1 June 1940, 3,500 Ross Rifles

Ross rifle

The Ross rifle was a straight-pull bolt-action 0.303 inch calibre rifle produced in Canada from 1903 until the middle of the First World War....

, which had last seen service in 1916, 72,384 rounds of .303 ammunition

.303 British

.303 British, or 7.7x56mmR, is a .311 inch calibre rifle and machine gun cartridge first developed in Britain as a blackpowder round put into service in December 1888 for the Lee-Metford rifle, later adapted to use smokeless powders...

 were received from the military and were distributed among divisions. Thames

River Thames

The River Thames flows through southern England. It is the longest river entirely in England and the second longest in the United Kingdom. While it is best known because its lower reaches flow through central London, the river flows alongside several other towns and cities, including Oxford,...

 division had the smallest rifle allocation with 61, and "S" Division the largest with 190. Fifty rifles were also issued to the London Fire Brigade

London Fire Brigade

The London Fire Brigade is the statutory fire and rescue service for London.Founded in 1865, it is the largest of the fire services in the United Kingdom and the fourth-largest in the world with nearly 7,000 staff, including 5,800 operational firefighters based in 112 fire...

, and Port of London Authority Police

Port of Tilbury Police

The Port of Tilbury Police is a small, specialised police force responsible for policing the Port of Tilbury, owned by the Port of Tilbury London Ltd, a subsidiary of Forth Ports plc. Known before 1992 as the Port of London Authority Police, at over 200 years old, it claims to be the oldest police...

.

Guns, petroleum and poison

In 1940, weapons were critically short; there was a particular scarcity of anti-tank weapons, many of which had been left in France. Ironside had only 170 2-pounder anti-tank guns

Ordnance QF 2 pounder

The Ordnance QF 2-pounder was a British anti-tank and vehicle-mounted gun, employed in the Second World War. It was actively used in the Battle of France, and during the North Africa campaign...

, but these were supplemented by 100 Hotchkiss 6-pounder guns dating from the First World War, improvised into the anti-tank role by the provision of solid shot. By the end of July 1940, an additional 900 75mm field guns

75 mm Gun M1917

The 75 mm Gun Model of 1917 was an interim measure, based on the British QF 18 pounder, produced by the United States in World War I after it had decided to switch from to 75 mm calibre for its field guns.-History:...

 had been received from the USA,—the British were desperate for any means of stopping armoured vehicles.

One of the few resources not in short supply was petroleum oil; supplies intended for Europe were filling British storage facilities. Considerable effort and enthusiasm was put into making use of petroleum products as a weapon of war. The Army had not had flame-throwers since the First World War, but a significant number were improvised from pressure greasing equipment acquired from automotive repair garages. Although limited in range, they were reasonably effective.

There were many ideas for using petroleum on a larger scale and although many proved fruitless a number of practical weapons were developed.

A mobile flame trap comprised surplus bulk storage tanks on trucks, the contents of which could be hosed into a sunken road

Sunken lane

A sunken lane is a road which has over time fallen significantly lower than the land on either side. They are created incrementally by erosion, by water and traffic...

 and ignited. A static flame trap was prepared with perforated pipes running down the side of a road connected to a 600 imp gal (2,727.7 l; 720.6 US gal) elevated tank. Usually gravity sufficed but in a few cases a pump assisted in spraying the mixture of oil and petrol.

A flame fougasse

Flame fougasse

A flame fougasse is a weapon. It is a type of mine which uses an explosive charge to project burning liquid onto a target. The flame fougasse was developed by the Petroleum Warfare Department in Britain as an anti-tank weapon during the invasion crisis of 1940...

 comprised a 40 gallon light steel drum filled with petroleum mixture and a small, electrically detonated explosive. This was dug into the roadside with a substantial overburden and camouflaged. Ammonal

Ammonal

Ammonal is an explosive made up of ammonium nitrate, trinitrotoluene , and aluminium powder.The ammonium nitrate functions as an oxidizer and aluminium as a power enhancer. To some extent the aluminium makes it more sensitive to detonation...

 provided the propellant charge, it was placed behind the barrel and, when triggered, caused the barrel to rupture and shoot a jet of flame 10 feet (3 m) wide and 30 yards (27.4 m) long. They were usually deployed in batteries of four barrels and would be placed at a location such as a corner, steep incline or roadblock where vehicles would be obliged to slow.

Variants of the flame fougasse included the demigasse, a barrel on its side and left in the open with explosive buried underneath; and the hedge hopper: a barrel on end with explosive buried underneath a few inches deep and slightly off centre. On firing, the hedge hopper barrel was projected ten feet (3 m) into the air and over a hedge or wall behind which it had been hidden. 50,000 flame fougasse barrels were installed at 7,000 sites mostly in southern England and at a further 2,000 sites in Scotland.

Early experiments with floating petroleum on the sea and igniting it were not entirely successful: the fuel was difficult to ignite, large quantities were required to cover even modest areas and the weapon was easily disrupted by waves. However, the potential was clear. By early 1941 a flame barrage technique was developed. Rather than attempting to ignite oil floating on water, nozzles were placed above high-water mark with pumps producing sufficient pressure to spray fuel which produced a roaring wall of flame over, rather than on, the water. Such installations consumed considerable resources and although this weapon was impressive, its network of pipes was vulnerable to pre-landing bombardment; General Brooke did not consider it effective. Initially ambitious plans were cut back to cover just a few miles of beaches.

It seems likely the British would have used poison gas against troops on beaches. General Brooke, in an annotation to his published war diaries, stated that he "...had every intention of using sprayed mustard gas on the beaches". Mustard gas was manufactured as well as chlorine

Chlorine

Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

, phosgene

Phosgene

Phosgene is the chemical compound with the formula COCl2. This colorless gas gained infamy as a chemical weapon during World War I. It is also a valued industrial reagent and building block in synthesis of pharmaceuticals and other organic compounds. In low concentrations, its odor resembles...

 and Paris Green

Paris Green

Paris Green is an inorganic compound more precisely known as copper acetoarsenite. It is a highly toxic emerald-green crystalline powder that has been used as a rodenticide and insecticide, and also as a pigment, despite its toxicity. It is also used as a blue colorant for fireworks...

. Poison gases were stored at key points for use by Bomber Command and in smaller quantities at many more airfields for use against the beaches. Bombers and crop sprayers would spray landing craft and beaches with mustard gas and Paris Green.

Deception and disinformation

In addition to hiding real weapons and fortifications, steps were taken to create the impression of the existence of defences that were not real. Drain pipes stood in place of real guns, dummy pillboxes were constructed, and uniformed mannequins kept an unblinking .

Volunteers were encouraged to use anything that would delay the enemy. A young member of the Home Guard (LDV) recalled:
In 1938, a section funded by MI6 was created for propaganda

Propaganda

Propaganda is a form of communication that is aimed at influencing the attitude of a community toward some cause or position so as to benefit oneself or one's group....

, headed by Sir Campbell Stuart. It was allocated premises at Electra House and was dubbed Department EH. On 25 September 1939 the unit was mobilised to Woburn Abbey

Woburn Abbey

Woburn Abbey , near Woburn, Bedfordshire, England, is a country house, the seat of the Duke of Bedford and the location of the Woburn Safari Park.- Pre-20th century :...

 where it joined a subversion team from MI6, known as Section D, and by July these teams became a part of the newly created Special Operations Executive

Special Operations Executive

The Special Operations Executive was a World War II organisation of the United Kingdom. It was officially formed by Prime Minister Winston Churchill and Minister of Economic Warfare Hugh Dalton on 22 July 1940, to conduct guerrilla warfare against the Axis powers and to instruct and aid local...

 (SOE). These SOE elements went on to form the core of the Political Warfare Executive

Political Warfare Executive

During World War II, the Political Warfare Executive was a British clandestine body created to produce and disseminate both white and black propaganda, with the aim of damaging enemy morale and sustaining the morale of the Occupied countries....

 in 1941. Their task was to spread false rumours and conduct psychological warfare

Psychological warfare

Psychological warfare , or the basic aspects of modern psychological operations , have been known by many other names or terms, including Psy Ops, Political Warfare, “Hearts and Minds,” and Propaganda...

. Inspired by a demonstration of petroleum warfare, one false rumour stated that the British had a new bomb: dropped from an aircraft, it caused a thin film of volatile liquid to spread over the surface of the water which it then ignited. Such rumours were credible and rapidly spread. American broadcaster William Shirer recorded large numbers of burns victims in Berlin; though it is not clear what he personally saw, it seems likely his reports were influenced by rumours. The interrogation of a Luftwaffe pilot revealed the existence of such weapons was common knowledge, and documents found after the war showed the German high command were deceived. The rumour seemed to take on a life of its own on both sides leading to persistent stories of a thwarted German invasion, in spite of official British denials. On 15 December 1940, The New York Times ran a story claiming that tens of thousands of German troops had been 'consumed by fire' in two failed invasion attempts.

Planned resistance

Auxiliary Units were a specially trained and secret organisation that, in an invasion, would provide resistance behind enemy lines. Selected for aptitude and local knowledge, men were mostly recruited from the Home Guard—which also provided a cover for their existence. Organised into patrols of 4 to 8 men: each patrol was a self-contained cell, expected to be self-sufficient. Each patrol was provided with a concealed underground operational base, usually built in woodland and camouflaged.

Auxiliary Units were well-equipped and supplied with food for 14 days (their expected lifespan).

In addition, a network of civilian Special Duties personnel was recruited to provide an intelligence gathering service, spying on enemy formations and troop movements. Reports were to be collected from dead letter drops

Dead drop

A dead drop or dead letter box is a method of espionage tradecraft used to pass items between two individuals by using a secret location and thus does not require them to meet directly. Using a dead drop permits a Case Officer and his Agent to exchange objects and information while maintaining...

 and relayed by radio operators of the Royal Signals

Royal Corps of Signals

The Royal Corps of Signals is one of the combat support arms of the British Army...

 from secret locations.

The threat recedes

After the evacuation of Dunkirk, people believed that the threatened invasion could come at almost any time. German preparations would require at least a few weeks, but all defensive precautions were made with an extreme sense of urgency. In the summer of 1940, an invasion attempt could occur any time, but some times were rather more likely than others: the phase of the moon, the tides and, most of all, the weather were considerations. The weather deteriorates significantly after September, but an October landing was not out of the question. On 3 October, General Brooke wrote in his diary "Still no invasion! I am beginning to think that the Germans may after all not attempt it. And yet! I have the horrid thought that he may still bring off some surprise on us."

The Battle of Britain

Battle of Britain

The Battle of Britain is the name given to the World War II air campaign waged by the German Air Force against the United Kingdom during the summer and autumn of 1940...

 had been won and on 12 October 1940, unknown to the British, Hitler rescheduled Sealion

Operation Sealion

Operation Sea Lion was Germany's plan to invade the United Kingdom during the Second World War, beginning in 1940. To have had any chance of success, however, the operation would have required air and naval supremacy over the English Channel...

 for the spring of 1941. By that spring, the state of Britain’s defences had much improved, with many more trained and equipped men becoming available and field fortifications reaching a high state of readiness. With national confidence rising, the Prime Minister, Churchill, was able to say "We are waiting for the long promised invasion. So are the fishes..."

When Germany invaded the Soviet Union

Operation Barbarossa

Operation Barbarossa was the code name for Germany's invasion of the Soviet Union during World War II that began on 22 June 1941. Over 4.5 million troops of the Axis powers invaded the USSR along a front., the largest invasion in the history of warfare...

, on 22 June 1941, it became unlikely that there would be any attempted landing as long as that conflict was undecided—from the British point of view at the time the matter hung in the balance. In July 1941, construction of field fortifications was greatly reduced and concentration given to the possibility of a raid in force rather than a full-scale invasion.

On 7 December 1941, a Japanese carrier fleet launched a surprise air attack on the American fleet at Pearl Harbor

Attack on Pearl Harbor

The attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941...

; by way of the German declaration of war, the USA entered the war on Britain's side. With America's Germany first strategic policy, resources flooded into the UK, effectively ending the danger of invasion after two years.

Would the preparations have been effective?

General Brooke frequently confided his concerns to his private diary. When published, he included additional annotations written many years later:
The question of whether the defences would have been effective in invasion is vexed. In mid-1940, the preparations relied heavily upon field fortifications. The First World War made it clear that assaulting prepared defences with infantry was deadly and difficult, but similar preparations in Belgium had been overrun by well-equipped German Panzer divisions in the early weeks of 1940 and with so many armaments left at Dunkirk, British forces were woefully ill-equipped to take on German armour. On the other hand, while British preparations for defence were ad hoc, so were the German invasion plans: a fleet of 2,000 converted barges and other vessels had been hurriedly made available and their fitness was debatable; in any case, the Germans could not land troops with all their heavy equipment. Until the Germans captured a port, both armies would have been short of tanks and heavy guns.

The later experiences of the Canadian Army during the disastrous Dieppe Raid

Dieppe Raid

The Dieppe Raid, also known as the Battle of Dieppe, Operation Rutter or later on Operation Jubilee, during the Second World War, was an Allied attack on the German-occupied port of Dieppe on the northern coast of France on 19 August 1942. The assault began at 5:00 AM and by 10:50 AM the Allied...

 of 1942, American forces on Omaha Beach

Omaha Beach

Omaha Beach is the code name for one of the five sectors of the Allied invasion of German-occupied France in the Normandy landings on 6 June 1944, during World War II...

 on D-day and taking on Japanese

Empire of Japan

The Empire of Japan is the name of the state of Japan that existed from the Meiji Restoration on 3 January 1868 to the enactment of the post-World War II Constitution of...

 defenders on Pacific Islands

Pacific Islands

The Pacific Islands comprise 20,000 to 30,000 islands in the Pacific Ocean. The islands are also sometimes collectively called Oceania, although Oceania is sometimes defined as also including Australasia and the Malay Archipelago....

 showed that under the right conditions, a defender could exact a terrible price from assaulting forces, significantly depleting and delaying enemy forces until reinforcements could be deployed to appropriate places via the sea, and inland.

In the event of invasion, the Royal Navy would have sailed to the landing places, possibly taking several days. It is now known that the Germans planned to land on the southern coast of England; one reason for this site was that the narrow seas of the English Channel

English Channel

The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...

 could be blocked with mines

Naval mine

A naval mine is a self-contained explosive device placed in water to destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, an enemy vessel...

, submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s and torpedo boat

Torpedo boat

A torpedo boat is a relatively small and fast naval vessel designed to carry torpedoes into battle. The first designs rammed enemy ships with explosive spar torpedoes, and later designs launched self-propelled Whitehead torpedoes. They were created to counter battleships and other large, slow and...

s. While German naval forces and the Luftwaffe could have extracted a high price from the Royal Navy, they could not have hoped to prevent interference with attempts to land a second wave of troops and supplies that would have been essential to German success—even if, by then, the Germans had captured a port essential for bringing in significant heavy equipment. In this scenario, British land forces would have faced the Germans on more equal terms than otherwise and it was only necessary to delay the German advance, preventing a collapse until the German land forces were, at least temporarily, isolated by the Royal Navy and then mounting a counter attack.

Scholarly consideration of the likely outcome of invasion, including war games at Royal Military Academy Sandhurst

Royal Military Academy Sandhurst

The Royal Military Academy Sandhurst , commonly known simply as Sandhurst, is a British Army officer initial training centre located in Sandhurst, Berkshire, England...

 in 1974, agrees that while German forces would have been able to land and gain a significant beachhead

Beachhead

Beachhead is a military term used to describe the line created when a unit reaches a beach, and begins to defend that area of beach, while other reinforcements help out, until a unit large enough to begin advancing has arrived. It is sometimes used interchangeably with Bridgehead and Lodgement...

, intervention of the Royal Navy would have been decisive and, even with the most optimistic assumptions, the German army would not have penetrated further than GHQ Line

GHQ Line

The GHQ Line was a defence line built in the United Kingdom during World War II to contain an expected German invasion.The British Army had abandoned most of its equipment in France after the Dunkirk evacuation...

 and would have been defeated.

Following the failure to gain even local air superiority in the Battle of Britain, Operation Sea Lion was postponed indefinitely. Hitler and his generals were aware of the problems of an invasion. Hitler was not ideologically committed to a long war with Britain and many commentators suggest that German invasion plans were a feint never to be put into action.

While Britain may have been militarily secure in 1940, both sides were aware of the possibility of a political collapse. If the Germans had won the Battle of Britain, the Luftwaffe would have been able to strike anywhere in southern England and with the prospect of an invasion, the British government would have come under pressure to come to terms: the extensive anti-invasion preparations demonstrated to Germany and to the people of Britain that whatever happened in the air, the United Kingdom was both able and willing to defend itself.

See also

• British hardened field defences of World War II
  British hardened field defences of World War II
  British hardened field defences of World War II were small fortified structures constructed as a part of British anti-invasion preparations. They were popularly known as pillboxes by reference to their shape.-Design and development:...
  
  
• Evacuations of civilians in Britain during World War II
  Evacuations of civilians in Britain during World War II
  Evacuation of civilians in Britain during the Second World War was designed to save the population of urban or military areas in the United Kingdom from aerial bombing of cities and military targets such as docks. Civilians, particularly children, were moved to areas thought to be less at risk....
  
  
• Eastbourne Redoubt
  Eastbourne Redoubt
  Eastbourne Redoubt is a fort on what is now Royal Parade, Eastbourne, East Sussex, England.-History:The Redoubt was built between 1804 and 1810 to support the associated Martello towers in defending against the threat of an invasion by Napoleon. It has defended the Eastbourne coast for nearly 200...
  
   home of the Combined Service Museum
• Dymchurch Redoubt
  Dymchurch Redoubt
  Dymchurch Grand Redoubt is a fortification on the coast of Kent in England, built during the Napoleonic War as part of a large defensive scheme to protect the country from an expected French invasion.-Description:...
  
  
• Operation Lucid
  Operation Lucid
  Operation Lucid was a British plan to use fire ships to attack invasion barges that were gathering in ports on the northern coast of France in preparation for a German invasion of Britain in 1940...
  
  
• Atlantic Wall
  Atlantic Wall
  The Atlantic Wall was an extensive system of coastal fortifications built by Nazi Germany between 1942 and 1944 along the western coast of Europe as a defense against an anticipated Allied invasion of the mainland continent from Great Britain.-History:On March 23, 1942 Führer Directive Number 40...
  
  
• Operation Sealion Order of Battle
  Operation Sealion order of battle
  The German plan for a land invasion of England in 1940 was code-named Operation Sea Lion . This is the Operation Sea Lion order of battle for the modified German plan produced in August, 1940.-Heeresgruppe A:...
  
  
• Operation Sea Lion
• Keep Calm and Carry On
  Keep Calm and Carry On
  Keep Calm and Carry On was a poster produced by the British government in 1939 during the beginning of the Second World War, intended to raise the morale of the British public in the event of invasion. Seeing only limited distribution, it was little known...
  
  

Official documents

• Consolidated Instructions to Invasion Committees in England and Wales (July 1942) HM Government.

Collections

- an online archive of wartime memories contributed by members of the public and gathered by the BBC. - subscription required

Further reading

• Foot, William. The Battlefields That Nearly Were. Defended England 1940 (Stroud: Tempus Publishing 2006) ISBN 978-0-7524-3849-8
• Osborne, Mike. 20th Century Defences in Britain (Stroud: Tempus Publishing 2003) ISBN 0-9540378-1-2
• Bird, C. Silent Sentinels - A study of the fixed defences constructed in Norfolk during WWI and WWII (Dereham: The Larks Press 1999) ISBN 0-948400-81-1
• Ross, Stewart. World War II Britain. History from Buildings (London: Franklin Watts 2006) ISBN 0-7496-6468-1
• Kauffmann, J.E. and Jurga, Robert M. Fortress Europe: European Fortifications of World War II, Da Capo Press, 2002. ISBN 0-306-81174-X

External links

• The German Threat to Britain in World War Two. By Dan Cruickshank
  Dan Cruickshank
  Dan Cruickshank is an art historian and BBC television presenter.-Early life:As a young child he lived for some years in Poland...
  
  . BBC website.
• The Real Dad's Army - TV Documentary.
• Churchill's mysterious map.
• Pillboxesuk.co.uk.
• Defence of Britain database.

54°0′13.176"N 2°32′52.278"W Landmarks centre of Great Britain