Halifax Explosion: The Largest Man-Made Explosion Before Atomic Bombs

When our minds pass over the carnage of World War One, we don't expect those scenes to be in Canada. Nova Scotia should have been safe. It was over 3000 miles from the front line, with the expanse of the Atlantic Ocean in between.

But that's to display marked ignorance about Canada's role in the Great War.

The country is part of the Commonwealth. It shares a monarch with Great Britain. Canadians had been fighting on the Western Front since war was declared in 1914.

Moreover, Canada was far enough away from Europe that its munition factories stood less chance of being destroyed by enemy action. It was accordingly a huge exporter of weaponry and explosives for the use of Allied forces.

The majority of those enlisted men and munitions alike sailed from Halifax Harbour. It was a fact not lost on the Germans. U-Boat submarines were common threats in those waters by 1917. Ships heading for the front line went under escort by naval destroyers, sailing in convoy across the Atlantic.

That was why SS Mont-Blanc was in the harbor on December 6th 1917. She was there to join her naval convoy.

As for Halifax itself, war had swelled the city's population to 65,000 people. Not least because Halifax was home to the headquarters of the Canadian Navy, and the first port of call for Canadian soldiers returning from the front line.

There was a lot of work in the docklands, as the harbor became the Allied central point for the whole of North America. Even ships headed for the USA had to call in there first for inspection.

That was why SS Imo was even in port on the day of the disaster. A Norwegian ship commissioned by the Committee for the Relief of Belgium, it had left Rotterdam in the Netherlands bound for New York. But wartime regulations sent it via Halifax.

It was not German U-Boats which caused the world's largest man-made pre-Atomic blast. That was an accident borne of frustration and human error.

It was perhaps understandable that Captain Haakon From of the SS Imo was feeling frustrated.

There were people dying in Belgium and he was caught up in British-Canadian bureaucracy. As a Norwegian captain sailing from a neutral Dutch port, there was really no need to take the lengthy detour into Canada. Except war-time regulations and the British saying so.

Meanwhile the relief supplies that would save the Belgians were sitting in New York. The SS Imo still had to get there - a voyage of two days - then cross the Atlantic once more. Captain From was keenly aware that this time-wasting diversion would be costing lives back in Belgium.

They'd been delayed for two days in Halifax Harbour, while administrators dealt with the paperwork. Then stopped from leaving once again, because the Halifax dockers hadn't delivered his refuel supply of coal in time before the nets came down.

That great long net barrier, held high in the waters by a row of buoys, was the harbor's night-time defense against German submarines. No-one left nor entered during the hours that it was up.

Also caught out by the barrier was Captain Aimé Le Medec of the SS Mont-Blanc. On the night of December 5th 1917, his ship had been stopped on the other side of it.

The French Captain had good reason to feel very nervous about this. His cargo hold and deck alike were filled with munitions destined for the front line. They were carrying 2366.5 tons of picric acid (wet and dry); 250 tons of TNT; 62.1 tons of gun cotton; and 246 tons of benzol. Oh! And 300 rounds of ammunition for the ship's own guns.

SS Mont-Blanc had been forced to sit out in the open ocean all night long, the crew alert for any sign of German submarines.

It was naturally with some relief that Captain Le Medec watched the defensive barrier being lifted, enabling him to finally sail into Halifax Harbour.

There is no doubt that Captain From was in a hurry to leave. He'd ordered the SS Imo to almost double the knots permitted for traveling through Halifax Harbour.

His ship's speed became even more of a hazard, because he was sailing out of the Bedford Basin. It was into an area of the harbor which closed in on itself, leading to a notorious stretch of waterway known locally as The Narrows.

The clue to its dimensions is in its name.

But SS Imo was able to move quickly. It had nothing in its hold. Those desperately needed relief supplies for Belgium were still many nautical miles away in New York.

Suddenly Captain From saw an American ship, the SS Clara, sailing towards him on the wrong side of the channel. All vessels were supposed to pass port to port. Captain Edward Renner, in his infinite wisdom, had decided to go starboard.

However the two captains were old friends. They communicated by loud-hailer. Instead of the expected exchange of tense words, the men jovially agreed to just by-pass regulations and sail starboard to starboard.

The maneuver sent SS Imo further east than it had the clearance to be. It put the ship right into the path of the tugboat Stella Maris and both of its attendant stows. Its captain, Horatio Brannen, later testified that the Norwegian ship was traveling at well over seven knots at that point. Way more than health and safety allowed.

Stella Maris, as the smaller, faster boat, was able to move quickly out of the way. Captain Brannen gave his order for the tugboat and its stows to shift towards the Halifax shore to avoid an accident.

On board the SS Imo, Captain From was also taking evasive action. He steered his ship into the opposite direction, closer to Dartmouth and even further east than before.

That's when he heard and saw the SS Mont-Blanc coming ponderously towards them.

The French munitions ship had never been fast. It certainly wasn't able to change course swiftly with its cargo so thoroughly over-laden, and it was traveling so very low in the water that day.

Halifax Harbour pilot Francis Mackey was on board the SS Mont-Blanc - and had been overnight - he recognized the danger posed by the SS Imo's current course. Long experience told him that the two ships would meet head on.

Mackey pulled on the ship's horn once - the universal signal for 'get out of the way'.

So far east, the SS Imo was trapped between on-coming ship and the Dartmouth shallows. It too would struggle to switch channels. Captain From ordered his deputy to blast their horn twice - 'no, I'm staying in this channel.'

Fully aware of every single implication of this collision, Mackey blasted the SS Mont-Blanc's horn once more. But he'd only just noticed another complication.

Both vessels immediately cut their engines. SS Imo was no longer traveling at speed towards disaster, but sheer inertia and current were still bringing the ships ever closer.

The easiest way to avoid crashing would have been for the SS Mont-Blanc to beach itself in the shallows. But Captain Le Medec dared not do that. It might cause a jolt which could set off a spark. His crew were banned from smoking or owning matches in order to prevent such a thing. Sparks could well be fatal on that particular ship.

However Pilot Mackey had twenty-four years' experience of these waters. He knew the harbor and he knew ships. He worked out how to save them from crashing.

Mackey ordered the SS Mont-Blanc to steer hard to port. The great, heavy ship labored, but eventually lumbered slightly to the side. For heart-stopping moments, all on board stared at the side of the SS Imo.

It was ridiculously close, but they were going to miss. The Norwegian ship was going to run parallel, just feet away from them.

But Captain From was also an experienced sailor and he'd set in motion a plan of his own to avoid collision. It was one which would interfere with Mackey's efforts with deadly results.

Three blasts on the horn from the SS Imo signaled that it was about to reverse. That would have worked brilliantly, if the SS Mont-Blanc wasn't suddenly sliding towards them on a parallel course. As it was, the reverse thrust of the Imo's right propeller, coupled with their light-weight condition due to the empty hold, caused the Norwegians to veer closer.

The prow of the SS Imo cut nine feet into the side of the SS Mont-Blanc, slicing straight into its number one hold. Within seconds, the engines - already set in gear - caused the Norwegian ship to disengage backwards.

Sparks flew onto the deck of the French vessel, right onto the benzol puddles, created when the jolt of collision upturned their barrels.

What happened next would destroy the reputations of some and make heroes of others. Disaster on the scale that occurred was not yet inevitable, but it would happen anyway.