A barrel bomb is a type of improvised explosive device (IED). Sometimes described as a "flying IED", they are made from a large barrel-shaped metal container that has been filled with high explosives, with possibly shrapnel, oil or chemicals, and then dropped from a helicopter or airplane.[1] Due to the large amount of explosives (up to thousands of pounds), their poor accuracy and indiscriminate use in populated civilian areas (including refugee camps), the resulting detonations have been devastating.[2][3][4] Critics have characterized them as weapons of terror and illegal under international conventions.The earliest known use of barrel bombs in their current form was in Croatia in 1991, where they were deployed from An-2 agricultural airplanes against Serbian positions around Vukovar. They were also used in Sudan in the 1990s, where they were rolled out of cargo-doors of transport planes. Barrel bombs have been used extensively by the Syrian Air Force during the Syrian Civil War and later by the Iraqi forces during Anbar clashes. Experts believe they will continue to be embraced by unstable nations fighting insurgencies since they are cheap to make and utilise the advantages of a government's air-power.[5]