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

by JoHarrington

1600 dead. Over 9000 injured. 400 permanently blinded. One of the greatest single day disasters of the First World War didn't happen on the front line, but in Canada.

On December 6th 1917, just after 9am, the city of Halifax blew up.

While every building in the city received some damage, those within a half mile radius of ground zero were completely obliterated. A wave of aftershock air pressure bent tree trunks double miles away.

For a moment there, the sea-bed of Halifax Harbour was exposed, as water was pushed back in the blast. Then it came again as a tsunami, wiping through all the towns, cities and settlements around the harbor.

The entire Fire Brigade had been killed outright. Fires raged across the whole of Halifax. One of the three hospitals had been wiped from the Earth. Another had half collapsed.

Just out to sea was a ship bringing over 1000 wounded Canadian soldiers from the Western Front, destined for the city's military hospital. And the heaviest snow blizzard in a decade was on the way.

Halifax coped. What other option did it have?

Canada During World War One

Canadians contributed a great deal to the war effort, including sending 620,000 men to the Western Front. Halifax was North America's main war-time seaport.

Image: Halifax, Nova Scotia 1900When 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.

History Books about Canada in the First World War

A Disastrous Collision in Halifax Harbour

One captain was irritated at the endless bureaucracy and details. Another had spent a nervous night worried about being blown to smithereens.

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.

Image: Defensive nets across Halifax Harbour during World War One
Image: Defensive nets across Halifax Harbour during World War One

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.

Image: The SS Imo in Halifax Harbour
Image: The SS Imo in Halifax Harbour

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.

Image: The SS Mont-Blanc
Image: The SS Mont-Blanc

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.

There was no red munitions flag - as international law demanded there should be - to give warning as to what was in the hold.

Because if you were the SS Mont-Blanc's captain, anchored overnight in a cove accessible from the open ocean, would you advertise your cargo to any patrolling U-Boat? Captain Le Medec had then forgotten to raise the red flag in the morning, before entering Halifax Harbour.

Captain From could not know the capabilities of the vessel before him. He had no inkling what the French ship was carrying. He answered with two more blasts. He was not changing course.

By the time he realized that the SS Mont-Blanc couldn't (or wouldn't) either, it was too late. With horrific slow motion they looked set to collide.

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.

Could the Canadian port of Halifax have been saved, if more had been done in those desperate last minutes before the catastrophic explosion of 1917?

History Books about the Halifax Disaster of 1917

Discover for yourself the fascinating - and heart-breaking - story of the World War One explosion that destroyed a Canadian city.
Blizzard of Glass: The Halifax Explosion of 1917

On December 6, 1917, two ships collided in Halifax Harbour. One ship was loaded top to bottom with munitions and the other held relief supplies, both intended for wartorn Europe...

View on Amazon

Curse of The Narrows: The Halifax Disaster of 1917

The dramatic story of one of the greatest disasters in historyIn 1917, the port of Halifax, Nova Scotia, was crowded with ships leaving for war-torn Europe. On December 6th, two...

View on Amazon

Explosion in Halifax Harbour: The illustrated account of a disaster that shook the world

The first illustrated book with full-colour visuals giving a compelling account of the explosion and its aftermath.On the morning of December 6, 1917, the residents of Halifax's...

View on Amazon

Too Many to Mourn: One Family's Tragedy in the Halifax Explosion

Forty-six members of the Jackson family were lost in the Halifax Disaster of 1917. A surviving relative gives an eye-witness account and tells their stories.

View on Amazon

The Halifax Explosion and the Royal Canadian Navy: Inquiry and Intrigue (Studies in Canadian Mili...

The Halifax Explosion of 1917 is a defining event in the Canadian consciousness, yet it has never been the subject of a sustained analytical history. Astonishingly, until now no...

View on Amazon

Town That Died (Nimbus classics)

A fact filled account of the greatest disaster to befall a Canadian city.

View on Amazon

Updated: 03/19/2014, JoHarrington
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blackspanielgallery on 06/14/2015

Incredibly interesting account, and well told.

JoHarrington on 03/17/2014

I hope it lives up to expectation. :)

WordChazer on 03/17/2014

Cliffhanger...now to part 2.

JoHarrington on 03/11/2014

I've just done it. My 600th is in the bag. :)

ologsinquito on 03/11/2014

You really are close. It's hard to believe you've published 600 articles here.

JoHarrington on 03/11/2014

One more article. I always do my Tips and Tricks at 01, so the next will be at 601.

Awww! Bless you for noticing that I'm close though!

Mira on 03/11/2014

Wow. I'm assuming that between this and part two you will stop and take stock of what happened with you at Wizzley for the last 50 articles ;-) I've been waiting for this one for the past 10 articles :):)

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