The Halifax Explosion occurred on December 6, 1917, when the SS Mont-Blanc, a French munitions ship, collided with the SS Imo in Halifax Harbour, causing the largest man-made explosion prior to the atomic bomb. The blast devastated much of the city, killing nearly 2,000 people and injuring thousands more. Among the heroes of the disaster was railway dispatcher Vincent Coleman, who stayed behind to send warning messages to halt incoming trains, sacrificing his life but saving many others.