[1] On Thursday morning, December 6, 1917, she entered Halifax Harbour in Nova Scotia, Canada, laden with a full cargo of highly volatile explosives.

The Raylton Dixon & Co shipyard built Mont-Blanc in Middlesbrough, England, as Yard Number 460 for the Société Générale de Transport Maritime (SGTM).

[6] The vessel was fully loaded with the explosives TNT, picric acid, and guncotton in the hold, with barrels on deck containing the high-octane fuel benzole, which itself consisted mainly of the highly volatile and easily ignited hydrocarbons benzene and toluene.

[7] She intended to join a slow convoy gathering in Bedford Basin readying to depart for Europe, but was too late to enter the harbour before the submarine nets were raised.

[6] Ships carrying dangerous cargo were not allowed into the harbour before the war, but the risks posed by German submarines had resulted in a relaxation of regulations.

[13] He first spotted the outbound SS Imo when she was about 1.21 kilometres (0.75 mi) away and became concerned as her path appeared to be heading towards his ship's starboard side, as if to cut him off his own course.

[14][15][16] The captain ordered Mont-Blanc to halt her engines and angle slightly to starboard, closer to the Dartmouth side of the Narrows.

[17] Sailors on nearby ships heard the series of signals, and realizing that a collision was imminent, gathered to watch as Imo bore down on Mont-Blanc.

[20] While the damage to Mont-Blanc was not severe, it toppled barrels that broke open and flooded the deck with benzol that quickly flowed into the hold.

A fire started at the water line and travelled quickly up the side of the ship as the benzol spewed out from crushed drums on Mont-Blanc's decks.

Surrounded by thick black smoke, and fearing she would explode almost immediately, the captain ordered the crew to abandon ship.

[21][20] A growing number of Halifax citizens gathered on the street or stood at the windows of their homes or businesses to watch the spectacular fire.

[23] As the lifeboats made their way across the harbour to the Dartmouth shore, the abandoned ship continued to drift and beached herself at Pier 6 near the foot of Richmond Street.

[30] The inquiry's report of 4 February 1918 blamed Mont-Blanc's captain Aimé Le Médec, the ship's pilot Francis Mackey, and Commander F. Evan Wyatt, the Royal Canadian Navy's chief examining officer in charge of the harbour, gates, and antisubmarine defences, for causing the collision.

[33] All three men were charged with manslaughter and criminal negligence at a preliminary hearing heard by Stipendiary Magistrate Richard A. McLeod, and bound over for trial.

Mackey's lawyer, Walter Joseph O'Hearn, asked a Nova Scotia Supreme Court justice, Benjamin Russell to issue a writ of habeas corpus.

[30] Subsequent appeals to the Supreme Court of Canada (19 May 1919), and the Judicial Committee of the Privy Council in London (22 March 1920), determined Mont-Blanc and Imo were equally to blame for navigational errors that led to the collision.

[40][42] Others are on display at the Maritime Museum of the Atlantic in Halifax, which has a large collection of Mont-Blanc fragments; many were recovered from the homes of survivors.