Halifax Explosion

In one of the worst human-made disasters in history, the explosion of an ammunition ship nearly destroyed the city of Halifax and killed nearly two thousand people.

Summary of Event

Halifax became an important North Atlantic shipping center during World War I. Merchant ships from around the world passed through Halifax, bound for war-torn Europe. These ships congregated in Halifax before British warships convoyed them across waters infested with German U-boats, and as a result Halifax became one of the busiest ports in the world. Wartime demands led to modernizations in Halifax’s harbor facilities, and the city had all the markings of a boomtown. Mont Blanc explosion
Disasters;Halifax explosion
Halifax explosion
[kw]Halifax Explosion (Dec. 6, 1917)
[kw]Explosion, Halifax (Dec. 6, 1917)
Mont Blanc explosion
Disasters;Halifax explosion
Halifax explosion
[g]Canada;Dec. 6, 1917: Halifax Explosion[04390]
[c]Disasters;Dec. 6, 1917: Halifax Explosion[04390]
[c]Transportation;Dec. 6, 1917: Halifax Explosion[04390]
From, Haakon
Hayes, William
Le Médec, Aimé[Lemédec, Aimé]
Mackey, Francis

Halifax’s narrow harbor was not easy to navigate: The town of Halifax was on the south side, and the community of Dartmouth was on the north side. Between the cities was a stretch of water, known as the Narrows, that connected the outer harbor with an inner harbor called Bedford Basin. Merchant ships making routine trips generally used the outer harbor, whereas ships awaiting convoy to Europe assembled in Bedford Basin. The harbor’s heavy traffic made the Narrows a hazardous place for ships to maneuver.

Halifax was known for potentially treacherous tides and weather, but the tides were moderate and the weather sunny as the French steamer Mont Blanc entered the Narrows on the morning of December 6, 1917. The ship was headed for Bedford Basin to join a convoy bound for Bordeaux two days later. Constructed in 1899, the 3,000-ton ship flew the flag of the French shipping company Compagne Générale Transatlantique. Its captain was Aimé Le Médec; harbor pilot Francis Mackey guided the ship into the Narrows. The Mont Blanc carried a dangerous cargo of 2,600 tons of American explosives (TNT, benzene, picric acid, and guncotton) destined for Allied armies in Europe. Ammunition ships typically flew red flags to warn other vessels of such dangerous cargo and to ensure that they were given a wide berth, but the Mont Blanc was not flying a red flag. Ammunition ships were prime targets for German submarines, and Captain Le Médec did not want to signal his cargo to any U-boats along the way.

At the same time the Mont Blanc was entering the Narrows, the 4,000-ton Norwegian steamship Imo
Imo (ship) was headed out to sea. A former passenger ship owned by the Belgium-based South Pacific Whaling Company, the Imo had been chartered by American relief agencies planning to distribute donated food and clothing to those suffering from the war in Europe. The Imo’s captain was Haakon From, and its harbor pilot was William Hayes. The Imo, empty of cargo, had arrived in Halifax from Rotterdam the previous day as part of a westbound convoy and was now headed for New York. Both ships, coming from opposite directions, entered the Narrows at 7:30 a.m. Either Le Médec or Mackey spotted the Imo and signaled to the ship that the Mont Blanc intended to pass on the wrong side; that is, on the starboard side instead of the traditional passing down the port side. This was contrary to established maritime procedure, but it was easier for ships entering the harbor to dock in Halifax on the south side of the Narrows by passing outbound ships on the left. At 8:15 a.m., the tugboat Stella Maris pulled away from the Halifax docks. The sudden appearance of the tugboat caused the Imo to turn to avoid a collision, placing it in the path of the Mont Blanc. The Mont Blanc sounded a blast of its steam whistle to signal its intention to maintain course. Unaware of the Mont Blanc’s hazardous cargo, the Imo responded with two steam-whistle blasts that announced the Imo’s claim of right-of-way and intention to continue on its course. Unwilling to yield, both ships reduced speed, but not enough to avoid a glancing collision.

The jolt, which occurred at 8:45 a.m., ruptured the benzene tanks on the Mont Blanc’s upper deck, and sparks from the scraping hulls caused the area to burst into flames. The Mont Blanc’s crew was unable to contain the fire, and rather than forcing the Mont Blanc to sink by flooding its explosive-filled holds—an act that might have prevented the looming catastrophe—they abandoned ship. The impact with the Imo caused the Mont Blanc to drift toward the shore and into the crowded city. The crews of the Stella Maris and the Royal Canadian Navy warship Niobe attempted to take the Mont Blanc under tow, but the ship drifted to the Halifax side of the Narrows. Innocent bystanders assembled to watch the events in the harbor, and many were killed and injured when, twenty minutes after the collision, the Mont Blanc exploded.

The eruption transformed the Mont Blanc into a storm of shrapnel: The half-ton anchor flew more than two miles. An enormous shockwave flattened more than two square miles of the city, and an eerie mushroom cloud rose three miles over Halifax. The explosion shattered windows ten miles away, and the detonation was felt on Prince Edward Island, which was more than one hundred miles away. Many small boats simply disappeared, and several larger vessels capsized. A fifteen-foot seismic wave crashed into the shattered shore, drowning many of those not killed outright in the blast. Fires, ignited by toppled coal stoves, spread out of control.

The detonation destroyed huge sections of Halifax. More than sixteen hundred buildings were leveled, and nearly half of Halifax’s population of roughly fifty thousand were homeless or lacked adequate shelter. To add to the city’s misery, a blizzard on December 7 seriously hampered relief efforts. In all, nearly two thousand residents of Halifax and Dartmouth died in the attack. Among the dead were half the crew of the Imo, including Captain From and Pilot Hayes. Only one crew member from the Mont Blanc died; Captain Le Médec and Pilot Mackey both survived.


The Halifax explosion was one of the world’s most devastating human-made disasters. The accident triggered the most powerful explosion in history up to that time and remained the largest nonnuclear explosion in history. Its destruction was alleviated, however, by the financial and humanitarian assistance that immediately flowed into Halifax. Ship captains at sea, either hearing or feeling the explosion from miles away, steamed toward Halifax. Relief trains from Boston plowed through the blizzard, arriving in time to save thousands of lives. In the months immediately after the blast, the Halifax Relief Commission received and disbursed nearly thirty million dollars’ worth of food, clothing, and supplies. Because of its importance as a wartime port, the reconstruction of Halifax and its harbor facilities became a priority for the Canadian and British governments. Temporary housing sheltered most of the city’s returning inhabitants until the city’s reconstruction after World War I.

No one was ever held responsible for the accident. A maritime investigation concluded that the Mont Blanc caused the collision but that the Imo was also partially responsible. Because both From and Hayes died in the explosion, however, prosecutors could offer only a limited amount of evidence, and although they charged Le Médec and Mackey with manslaughter, there was not enough evidence available to convict them. Le Médec returned to France, Mackey resumed his job as a harbor pilot, and Halifax tried to recover from its deadly blow. Mont Blanc explosion
Disasters;Halifax explosion
Halifax explosion

Further Reading

  • Armstrong, John G. The Halifax Explosion and the Royal Canadian Navy: Inquiry and Intrigue. Vancouver: University of British Columbia Press, 2002. A study of the Royal Canadian Navy that examines charges that the navy failed to adequately monitor and control the harbor and must accept some blame for the disaster.
  • Bird, Michael J. The Town That Died: The True Story of the Greatest Man-Made Explosion Before Hiroshima. New York: Putnam, 1962. The first major historical examination of the explosion.
  • Kitz, Janet F. Shattered City: The Halifax Explosion and the Road to Recovery. Halifax, N.S.: Nimbus, 1989. Using the explosion as an introduction, this work emphasizes Halifax’s postexplosion reconstruction and repopulation.
  • McDonald, Laura. Curse of the Narrows. New York: Walker, 2005. Concentrates on the explosion’s human cost and examines the explosion’s impact on common citizens. Also explores contemporary rumors that the explosion was the work of German saboteurs.

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