On the morning of 6 December 1917, the French cargo ship collided with the Norwegian vessel in the harbour of Halifax, Nova Scotia, Canada. The Mont-Blanc, laden with high explosives, caught fire and exploded, devastating the Richmond district of Halifax. At least 1,782 people were killed, largely in Halifax and Dartmouth, by the blast, debris, fires, or collapsed buildings, and an estimated 9,000 others were injured. The blast was the largest human-made explosion at the time. It released the equivalent energy of roughly .
Mont-Blanc was under orders from the French government to carry her cargo from New York City via Halifax to Bordeaux, France. At roughly 8:45 am, she collided at low speed, approximately one knot (), with the unladen Imo, chartered by the Commission for Relief in Belgium to pick up a cargo of relief supplies in New York. On the Mont-Blanc, the impact damaged benzol barrels stored on deck, leaking vapours which were ignited by sparks from the collision, setting off a fire on board that quickly grew out of control. Approximately 20 minutes later at 9:04:35 am, the Mont-Blanc exploded.
Nearly all structures within an 800-metre (half-mile) radius, including the community of Richmond, were obliterated. A pressure wave snapped trees, bent iron rails, demolished buildings, grounded vessels (including Imo, which was washed ashore by the ensuing tsunami), and scattered fragments of Mont-Blanc for kilometres. Across the harbour, in Dartmouth, there was also widespread damage. A tsunami created by the blast wiped out the community of the Mi'kmaq First Nation who had lived in the Tufts Cove area for generations.
Relief efforts began almost immediately, and hospitals quickly became full. Rescue trains began arriving the day of the explosion from across Nova Scotia and New Brunswick while other trains from central Canada and the Northeastern United States were impeded by blizzards. Construction of temporary shelters to house the many people left homeless began soon after the disaster. The initial judicial inquiry found Mont-Blanc to have been responsible for the disaster, but a later appeal determined that both vessels were to blame. The North End of Halifax has several memorials to the victims of the explosion.
Background
Dartmouth lies on the east shore of Halifax Harbour, and Halifax is on the west shore. By 1917, "Halifax's inner harbour had become a principal assembly point for merchant convoys leaving for Britain and France." Halifax and Dartmouth had thrived during times of war; the harbour was one of the British Royal Navy's most important bases in North America, a centre for wartime trade, and a home to privateers who harried the British Empire's enemies during the American Revolution, the Napoleonic Wars, and the War of 1812.
The completion of the Intercolonial Railway and its Deep Water Terminal in 1880 allowed for increased steamship trade and led to accelerated development of the port area, but Halifax faced an economic downturn in the 1890s as local factories struggled to compete with businesses in central Canada. The British garrison left the city in late 1905 and early 1906. The Canadian government took over the Halifax Dockyard (now CFB Halifax) from the Royal Navy. This dockyard later became the command centre of the Royal Canadian Navy upon its founding in 1910.
Just before the First World War, the Canadian government began a determined, costly effort to develop the harbour and waterfront facilities. The outbreak of the war brought Halifax back to prominence. As the Royal Canadian Navy had virtually no seaworthy ships of its own, the Royal Navy assumed responsibility for maintaining Atlantic trade routes by re-adopting Halifax as its North American base of operations. In 1915, management of the harbour fell under the control of the Royal Canadian Navy; by 1917 there was a growing naval fleet in Halifax, including patrol ships, tugboats, and minesweepers.
The population of Halifax/Dartmouth had increased to between 60,000 and 65,000 people by 1917. Convoys carried men, animals, and supplies to the European theatre of war. The two main points of departure were in Nova Scotia at Sydney, on Cape Breton Island, and Halifax. Hospital ships brought the wounded to the city, so a new military hospital was constructed.
The success of German U-boat attacks on ships crossing the Atlantic Ocean led the Allies to institute a convoy system to reduce losses while transporting goods and soldiers to Europe. Merchant ships gathered at Bedford Basin on the northwestern end of the harbour, which was protected by two sets of anti-submarine nets and guarded by patrol ships of the Royal Canadian Navy.