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Thermos bomb - Italian
A cross section of the bomb
Type Aerial bomb
Place of origin Italy
Service history
Used by Italy
Wars World War II
Weight 3.68 kg
Length 12.3 inches
Diameter 2.75 inches

Filling TNT
Filling weight 0.67 kg
Anti-handling device

Thermos bomb was the informal name for the AR-4, an air dropped anti-personnel mine used by the Italian Air Force during World War II. Large numbers were used against Malta and in the Middle East. It was named for its superficial appearance to a Thermos bottle, a popular brand of vacuum flask. The bomb was a cylinder 31 centimetres long and weighing 3.68 kilograms. It could be fitted with a very sensitive motion-sensitive fuze that would detonate if any attempt was made to move it, and could be lethal in the open up to around 35 metres away. Because of this, unexploded Thermos bombs were normally destroyed where they fell, generally by attaching a long piece of string to them and giving it a jerk, or detonating a small explosive charge next to them.

A later variant of the fuze introduced an additional time delayed detonation, which was triggered between 60 to 80 hours after the fuze had armed.


  • Italian and French Explosive Ordnance. Bu-ord. 14 June 1946. 

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