''Thermos bomb'' was the informal name for the AR-4, an air dropped anti-personnel mine used by the

Italian Air Force , colours = , colours_label = , march = (Ordinance March of the Air Force) by Alberto Di Miniello , mascot = , anniversaries = 28 March ...

during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

. Large numbers were used against

Malta Malta ( , , ), officially the Republic of Malta ( mt, Repubblika ta' Malta ), is an island country in the Mediterranean Sea. It consists of an archipelago, between Italy and Libya, and is often considered a part of Southern Europe. It lies ...

and in the

Middle East The Middle East ( ar, الشرق الأوسط, ISO 233: ) is a geopolitical region commonly encompassing Arabia (including the Arabian Peninsula and Bahrain), Asia Minor (Asian part of Turkey except Hatay Province), East Thrace (Europ ...

. It was named for its superficial appearance to a

Thermos A vacuum flask (also known as a Dewar flask, Dewar bottle or thermos) is an insulating storage vessel that greatly lengthens the time over which its contents remain hotter or cooler than the flask's surroundings. Invented by Sir James Dewa ...

bottle, a popular brand of

vacuum flask A vacuum flask (also known as a Dewar flask, Dewar bottle or thermos) is an insulating storage vessel that greatly lengthens the time over which its contents remain hotter or cooler than the flask's surroundings. Invented by Sir James Dewa ...

. The bomb was a cylinder long and weighing . It could be fitted with a very sensitive motion-sensitive fuze that would

detonate Detonation () is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations propagate supersonically through shock waves with ...

if any attempt was made to move it. It could be lethal in the open to approximately . Because of this, unexploded Thermos bombs were normally destroyed where they fell, either by attaching a long piece of string to them and giving it a jerk, or detonating a small explosive charge near them. A later variant of the fuze introduced a long time delay, which triggered between 60 and 80 hours after the fuze had armed.

References

* Area denial weapons Anti-personnel weapons Italian inventions World War II aerial bombs of Italy Military equipment introduced from 1940 to 1944 {{Landmine-stub