The Home Guard was a defence organisation of the British Army during the Second World War

British Army during World War II

The British Army during the Second World War was, in 1939, a volunteer army, that introduced limited conscription in early 1939, and full conscription shortly after the declaration of war with Germany. During the early years of the war, the army suffered defeat in almost every theatre in which it...

. Operational from 1940 until 1944, the Home Guard—comprising 1.5 million local volunteers otherwise ineligible for military service, usually owing to age, hence the nickname 'Dad's Army' — acted as a secondary defence force, in case of invasion by the forces of Nazi 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...

 and their allies

Axis Powers

The Axis powers , also known as the Axis alliance, Axis nations, Axis countries, or just the Axis, was an alignment of great powers during the mid-20th century that fought World War II against the Allies. It began in 1936 with treaties of friendship between Germany and Italy and between Germany and...

. The Home Guard guarded the coastal areas of Britain and other important places such as airfields, factories and explosives stores.
The origins of the Home Guard can be traced to Captain Tom Wintringham

Tom Wintringham

Thomas Henry Wintringham was a British soldier, military historian, journalist, poet, Marxist, politician and author. He was an important figure in the formation of the Home Guard during World War II and was one of the founders of the Common Wealth Party.-Early life:Tom Wintringham was born 1898...

, who returned from the Spanish Civil War

Spanish Civil War

The Spanish Civil WarAlso known as The Crusade among Nationalists, the Fourth Carlist War among Carlists, and The Rebellion or Uprising among Republicans. was a major conflict fought in Spain from 17 July 1936 to 1 April 1939...

 and wrote a book entitled How to Reform the Army.