In Richmond Prison, at the end of Gottingen Street, Halifax, the warden's young son was drawn to a window by a spectacular display of fireworks. Too sick to go to school that day he had gone to work with his dad. Suddenly he was blinded by a brilliant flash of light and then stunned by an unearthly roar. He was one of the first eyewitnesses to Canada's greatest disaster, the Halifax Explosion. He ran in terror, screaming for his father.

In the pre-dawn darkness of Thursday, December 6, 1917, the French munitions ship Mont Blanc lay at anchor near the mouth of Halifax Harbour. It seemed a small, nondescript vessel, but it carried a deadly cargo, a witch's brew of picric acid (used to make artillery shells), TNT, guncotton, benzol (a high octane fuel) and live ammunition. The ship was prevented from entering the narrows the night before by the closing of the submarine net, the same net that prevented the Imo, a Norwegian relief ship bound for Belgium, from leaving. That morning, the two ships' captains were anxious to get going. The Imo was 18 hours behind schedule and the Mont Blanc was a sitting duck in the open harbour.

Twice the captain of the Imo avoided other vessels by passing on their starboard side, which was not standard procedure and brought the ship ever closer to the Dartmouth shore. There the pilot of the Mont Blanc was astonished to see the Imo advancing. The two ships exchanged a bewildering array of contradictory horn and whistle blasts. The last seconds before the collision dissolved in indecision and then panic.

Devastation after the Halifax explosion, showing what is left of the Richmond neighbourhood. The IMO can been seen beached on the far shore (The James Collection/City of Toronto Archives)

In a final, fatal maneuver both captains bellowed out orders to put their engines full speed astern. The Mont Blanc lurched sideways. The Imo's bow swung about and its stern struck the Mont Blanc. The grinding of ragged metal sprayed sparks and ignited the benzol. The Mont Blanc's crew dove into the lifeboats and rowed for dear life, shouting warnings that no-one could understand.

For the next 20 minutes the fiery spectacle of the Mont Blanc drew a crowd of wide-eyed onlookers as it drifted ominously across the harbour towards Pier Six. In the rail yards at Richmond Station, a telegraph operator tapped out a last telegraph message: "Munitions ship on fire in the harbour. Heading for Pier Six. Good Bye." Seconds later the Mont Blanc detonated. It was the world's greatest man-made explosion before Hiroshima. The mind numbing roar of the blast was heard as far away as Sable Island and Cape Breton.

A fireball as hot as the surface of the Sun rolled over the docks, vapourizing those within its range, as if they had never existed. The metal of the Mont Blanc shattered into millions of shards moving at a velocity greater than any bullet. A sailor, J.C. Meyers, who was only 30 metres away from the blast, heard someone call "Look out!" It was the last thing that he remembered until he found himself lying on the ground at Fort Needham, over a kilometer away, wearing nothing but his boots.

Behind the fireball came a blast of air a thousand times more powerful than any hurricane, compressing the air into a steel fist, tossing railway cars like toys, smashing houses like matchsticks and crushing anyone in its path. Behind the wall of air came a deadly shower of shrapnel. In the harbour, the Imo was stripped of its superstructure and beached on the far shore. Within two seconds of the explosion the entire neighborhood of Richmond was obliterated, leaving at least 1000 people dead.

In less time than it takes to draw a deep breath almost every building in Halifax and Dartmouth had been damaged. Early rescue efforts were chaotic. The city had no power and no way to tell the world. As the word of the disaster spread, medical aid, food, clothing, building materials and skilled labourers poured in from throughout the Maritimes, central Canada, New England and the world.

The official tally of the dead is 1963, but almost certainly more died. At least 9000 more were injured and 25,000 left homeless. The confusion in the city lasted months as those who had lost loved ones spent countless hours searching and asking questions that could never be answered. There was no measure for the grief. In one family alone, that of James and Elizabeth Jackson, 46 were killed and 19 injured.

Wartime suspicion led many to think that the explosion must be an act of sabotage. The Halifax Herald blamed it on "that arch criminal, the Kaiser of Germany." An early enquiry inexplicably put the whole blame on the captain and pilot of the Mont Blanc. The Supreme Court of Canada portioned the responsibility, with two judges blaming the Imo, two the Mont Blanc, and the fifth deciding each had acted imprudently.