Entering World War I’s fourth demoralizing year, the Allies hoped to break the grueling stalemate by sending thousands of fresh American troops and more munitions than ever to the trenches of France. Before the French freighter Mont-Blanc set sail from Brooklyn on December 1, 1917, with a staggering 3,000 tons of explosives, the captain banned his crew from lighting a single match, and secured the volatile cargo with copper nails because they don’t spark when struck.

For four harrowing days, the floating powder keg bobbed up the Eastern seaboard, plowing through a wicked snowstorm and waters infested with German U-Boats, which had already torpedoed a thousand Allied ships that year alone. On December 6, the exhausted crew finally slipped into Halifax Harbour -- just as the relief ship Imo was rushing to leave. At 8:45 a.m., the Imo struck the Mont-Blanc’s bow, knocking over barrels of airplane fuel. Fire swept across the decks, sending the Mont-Blanc&rs