A wartime ship collision caused the largest human-made blast before Hiroshima

On 6 December 1917, the French munitions ship Mont-Blanc collided with the Norwegian vessel Imo in Halifax Harbour, caught fire, and detonated roughly 2,900 tonnes of TNT-equivalent explosives. The blast flattened Halifax's Richmond district, killed around 1,800 people, and remained the largest artificial explosion on record until nuclear weapons tests began decades later.

— Laura M. MacDonald, Curse of the Narrows: The Halifax Explosion 1917 — Walker & Company, 2005
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