“On the morning of Thursday, Dec. 6, 1917, the captain and crew of a French munitions ship called Mont-Blanc were eager to reach the safety of Halifax Harbour, and with good reason,” writes John U. Bacon for The Boston Globe. The ship was chock-full of explosives for use against Germany. But before it could reach the harbour, you might say mistakes were made.

The ship exploded at in dock at a force estimated to be one-fifth that of the first atomic bomb.

About two hours after the explosion, Governor Samuel W. McCall sent a telegram to the mayor of Halifax: “Understand your city in danger from explosion and conflagration. Reports only fragmentary. Massachusetts ready to go the limit in rendering every assistance you may be in need of. Wire me immediately.”