Concertina wire or Dannert Wire is a type of barbed wire

Barbed wire

Barbed wire, also known as barb wire , is a type of fencing wire constructed with sharp edges or points arranged at intervals along the strand. It is used to construct inexpensive fences and is used atop walls surrounding secured property...

 or razor wire

Razor wire

Barbed tape or razor wire is a mesh of metal strips with sharp edges whose purpose is to prevent passage by humans. The term "razor wire", through long usage, has generally been used to describe barbed tape products...

 that is formed in large coils which can be expanded like a concertina

Concertina

A concertina is a free-reed musical instrument, like the various accordions and the harmonica. It has a bellows and buttons typically on both ends of it. When pressed, the buttons travel in the same direction as the bellows, unlike accordion buttons which travel perpendicularly to it...

. In conjunction with plain barbed wire and steel pickets

Picket fence

A picket fence is a variety of fence that has been used mostly for domestic boundaries. Until the introduction of advertising on fences in the 1980s, a Cricket field was also usually surrounded by a picket fence, giving rise to the expression rattling the pickets for a ball hit firmly into the...

, it is used to form military wire obstacle

Wire obstacle

In the military science of fortification, wire obstacles are defensive obstacles made from barbed wire, barbed tape or concertina wire. They are designed to disrupt, delay and generally slow down an attacking enemy...

s.

During World War I soldiers manufactured concertina wire themselves, using ordinary barbed wire. Today, it is factory made.

Origins

In the First World War, barbed wire obstacles were made by stretching lengths of barbed wire between stakes of wood or iron. At its simplest, such a barrier would resemble a fence as might be used for agricultural purposes. The double apron fence comprised a line of pickets with wires running diagonally down to points on the ground either side of the fence. Horizontal wires were attached to these diagonals.

More elaborate and formidable obstructions could be formed with multiple lines of stakes connected with wire running from side-to-side, back-to-front and diagonally in every possible direction. Effective as these obstacles were, their construction took considerable time.

Barbed wire obstacles were vulnerable to being pushed about by artillery shells, and in the First World War this frequently resulted in a mass of randomly entangled wires that could be even more daunting than a carefully constructed obstacle. Learning this lesson, First World War soldiers would deploy barbed wire in so-called concertinas that were relatively loose. Barbed wire concertinas could be pre-prepared in the trenches

Trench warfare

Trench warfare is a form of occupied fighting lines, consisting largely of trenches, in which troops are largely immune to the enemy's small arms fire and are substantially sheltered from artillery...

 and then deployed in no-man's-land relatively quickly under cover of darkness.
Concertina wire packs flat for ease of transport, but can then be deployed as an obstacle much more quickly than ordinary barbed wire.

A platoon

Platoon

A platoon is a military unit typically composed of two to four sections or squads and containing 16 to 50 soldiers. Platoons are organized into a company, which typically consists of three, four or five platoons. A platoon is typically the smallest military unit led by a commissioned officer—the...

 of soldiers can deploy a single concertina fence at a rate of about a kilometer per hour. Such an obstacle is not very effective by itself, and concertinas are normally built up into more elaborate patterns as time permits.

Today, concertina wire is factory made and is available in forms that can be deployed very rapidly from the back of a vehicle or trailer.

Dannert wire

Oil-tempered barbed wire was developed during the First World War; it was much harder to cut than ordinary barbed wire. During the 1930s, German Horst Dannert developed concertinas of this high-grade steel wire. The result was entirely self-supporting; it did not require any vertical posts. An individual Dannert wire concertina could be compressed into a compact coil that could be carried by one man and then stretched out along its axis to make a barrier 50 feet (15.2 m) long and each coil could be held in place with just three staples hammered into the ground.

Dannert wire was imported into Britain from Germany before the Second World War. During the invasion crisis of 1940-1941

British anti-invasion preparations of World War II

British anti-invasion preparations of the Second World War entailed a large-scale division of military and civilian mobilisation in response to the threat of invasion by German armed forces in 1940 and 1941. The British army needed to recover from the defeat of the British Expeditionary Force in...

, the demand for Dannert wire was so great that some was produced with low manganese steel wire which was easier to cut. This material was known as "Yellow Dannert" after the identifying yellow paint on the concertina handles. To compensate for the reduced effectiveness of Yellow Dannert, an extra supply of pickets were issued in lieu of screw pickets.

Triple concertina wire

A barrier known as a triple concertina wire fence consists of two parallel concertinas joined by twists of wire and topped by a third concertina similarly attached. The result was an extremely effective barrier with many of the desirable properties of a random entanglement. A triple concertina fence could be deployed very quickly: it is possible for a party of five men to deploy 50 yards (45.7 m) of triple concertina fence in just fifteen minutes. Optionally, triple concertina fence could be strengthened with uprights, but this increases the construction time significantly.

Constantine wire

Concertina wire is sometimes mistakenly called constantine wire. "Constantine" probably came from a corruption/misunderstanding of "Concertina" and led to confusion with the Roman Emperor Constantine. This in turn has led to some people trying to differentiate between concertina wire and "constantine" wire by assigning the latter term to what is commonly known as razor wire. In contrast to the double-helical construction of concertina wire, as shown being deployed by soldiers in the image, razor wire, or less commonly "constantine wire", consists of a single wire with projecting teeth periodically along its length.

General references