Hiding A Bomb In Plain Sight

During World War II, Britain's SOE developed a clever sabotage device: plastic explosives disguised as lumps of coal. Hand-painted to match local coal and weighted correctly, these fake coal bombs could be slipped into enemy coal stores by resistance fighters. Once shoveled into a boiler, the heat would trigger the explosion. The concept actually predates WWII — Confederate agent Thomas Edgeworth Courtenay built coal 'torpedoes' during the US Civil War in the 1860s, and similar devices were used by the OSS and even Axis powers. The primary strategic value was disrupting supply lines and forcing armies to divert soldiers to guard coal stocks.