A small WWII-era bomb with a magnesium alloy body and incendiary fill comprising a chemical called thermite. As it struck the ground, a percussion charge would ignite the thermite and the bomb.
The standard B1E type accounted for the majority of bomb loads, however some included a small explosive with a delay fuse. The inclusion of these models acted as a deterrence to anyone attempting to extinguish the bomb before it could fully ignite.
The incendiary component within the bomb burns aggressively at over 1,000°C, creating a significant burn hazard. As such, all models of these bombs should be considered dangerous, not just the explosive type.
Between 1940 and 1944 more than a million of these 1kg devices were dropped on Britain by Luftwaffe aircraft. They were dispersed by cluster bomb containers, holding up to 620 of the deadly sub-munitions.
As a result, the most commonly encountered unexploded Luftwaffe bombs in the U.K are the 1kg incendiary type.