STEVE INSKEEP, HOST:
And I'm Steve Inskeep with a story of a voyage at sea - a voyage that ended in an almost incomprehensible explosion 100 years ago today.
JOHN U. BACON: The journey starts in Gravesend Bay, N.Y., a beautifully named port.
INSKEEP: That's the author, John U. Bacon, who says it was 1917. World War I was underway. The United States was shipping munitions to its allies, Britain and France. As the war grew desperate, the Allies needed more.
Bacon wrote a book about what happened when crews filled a ship called the Mont-Blanc with high explosives.
BACON: They load up 6 million pounds of TNT and picric acid onto the ship.
INSKEEP: Picric acid?
BACON: Picric acid, actually, is worse than TNT by about 10 percent. Then crucially 400 barrels of airplane fuel, stacked hastily on the top of the ship - that will provide the fuse for this perfect bomb.
INSKEEP: The ship was bound for France and made a stop on the way. In early December, 1917, it approached the port city of Halifax on the eastern shore of Canada. Bacon's book, called "The Great Halifax Explosion," reconstructs what happened on December 6. The Mont-Blanc tried to steam through a narrow channel into the harbour at the same time that another ship, called the Imo, was coming the other way.
BACON: Now, the Imo is dying to get out and Mont-Blanc is dying to get in. So the Imo starts passing ships on its left again and again and again. That is against nautical convention. And it's like a rural road in the country, of course. When you keep on passing cars to the left, sooner or later you're going to find another car facing you, coming your way.
INSKEEP: That was the Mont-Blanc. The two ships collided - not a big deal. The ocean-going equivalent of a fender bender, except that the collision shook the cargo onboard the Mont-Blanc.
BACON: The problem is that hastily stacked airplane fuel, it falls over and it ignites. So now you got the fuse lit on this amazing bomb. The crew knows what they're carrying, so they say, we're out of here. They hop in their two rowboats and go to the other side of the harbor, away from the population, and run into the woods as far as they can get. And now you've got a ghost ship, and that ghost ship slides perfectly on its own into pier six at the base of Halifax Harbor. And that is tragic.
INSKEEP: Oh, went right toward the city with what looks like, from the outside, a fire - not a good thing, but not disastrous.
BACON: For the locals, it's amusing. All the kids are walking to school at 8:46 in the morning. All the people are walking to work. They all stop by pier six to see this thing. And occasionally, barrels of benzol fuel - the airplane fuel - get launched into the sky, and it's oohs and aahs like July Fourth fireworks.
INSKEEP: And then the fire reached the main cargo of explosives - the 6 million pounds of TNT, the picric acid. The explosion was the largest on record until the dropping of the atomic bombs in World War II.
BACON: This thing shot up a two-mile-high mushroom cloud, probably the world's first. And it was just an unbelievable cataclysm - one-fifth the power of the atomic bomb. A one-ton anchor flew four miles. A one-ton cannon flew three miles the other direction. Human beings were flown half a mile in all directions. Half of Halifax is gone - 25,000 are homeless, 9,000 are wounded and 2,000 are dead in that split second.
INSKEEP: And in the aftermath, an unlikely hero stepped forward to help - the United States.
BACON: Believe it or not, U.S. and Canada for 140 years were not allies. In 1776 and 1812, we fought against each other. Halifax secretly supported the Confederacy during the Civil War. And in 1911, the speaker of the house - the Paul Ryan of his day - gets on the floor of the U.S. Congress and advocates for the annexation of Canada and receives loud cheers and a very favorable write-up in The Washington Post.
INSKEEP: So not a great history, but when news of this explosion spread 100 years ago, Massachusetts Governor Samuel McCall sent trainloads of doctors, nurses and medical supplies to Halifax.
BACON: It was incredible. When the trains start showing up, these very stoic Canadians start crying, I mean, all across the city. And they made a city of convert's toward the American cause. And within a week, Woodrow Wilson and the prime minister of Canada are exchanging love letters on the front page of The New York Times. You would not have seen that six years earlier.
INSKEEP: And the gesture cemented an alliance between the two countries.
BACON: Halifax to this day still sends Boston - at a cost of $180,000 - a Christmas tree, the best one they can find in the province. And that's their way of thanking them for all the good deeds done 100 years ago by their great-grandparents. And even though a lot of folks in Boston don't know why they're being thanked, somebody in Halifax said, why should we stop thanking them?
INSKEEP: John U. Bacon's new book is called "The Great Halifax Explosion." Transcript provided by NPR, Copyright NPR.