The Treaty of Utrecht ending the War of the Spanish Succession in 1713 cost France heavily in the New World, but its smooth-talking diplomats salvaged one strategic point. This was Cape Breton Island, a rugged, lonely bit of real estate jutting out into the Atlantic Ocean off the tip of Nova Scotia. There France built the fortress of Louisbourg, renowned in the early eighteenth century as the strongest in North America and perhaps in the world.

Some twenty miles southeast of what is now the island city of Sydney, a narrowgated harbor faced the North Atlantic. About two miles long from northeast to southwest, with an average width of half a mile, the bay was usually clear of ice the year round and sheltered from ocean storms by two necks of land that pinched the entrance to less than a mile, although rocks and shoals restricted the navigable passage to less than half that. Near the middle of the harbor mouth sat a small island.

The shoreline was low and rock-strewn, lashed by heavy surf nine days out of ten, and blanketed by heavy fog for weeks at a time. The sea itself was a great moat, the coast a fogbound lee shore too dangerous for heavy warships to close within effective bombardment range.

After the French military engineers sited the fort on the southern headland, work went slowly. The project so taxed the French treasury that King Louis XV was said to have remarked that someday he expected to look out the window at Versailles and see the walls of Louisbourg thrusting above the horizon.

The walls of this typical eighteenth-century stronghold enclosed fifty-seven acres between the seashore and inner harbor that contained a complete town that eventually housed four thousand people, exclusive of the garrison. The most massive portion was on the land side facing south, an earth-filled wall twelve hundred yards long, thirty feet high, revetted with solid masonry a foot thick and anchored at each end with bastions. The biggest of Louisbourg’s bastions—the King’s Bastion—contained in its gorge a strongly built stone structure that was the largest building in North America at the time: four stories high and three hundred and sixty feet long. The enclosure had emplacements for 148 guns, although never more than 90 were in position.

On the island off the tip of the peninsula a powerful battery covered the channel, and another one, called the Grand Battery or Batterie Royale, swept the entrance head-on. When completely armed—it never really was—Louisbourg could mount more than two hundred heavy guns and twenty huge mortars.

The imposing facade, however, had fatal flaws. It was dominated by a series of low hills about half a mile to the southwest, from which besiegers could command the wall. Since the French didn’t believe heavy guns could be moved through miles of swamp to the position, they didn’t bother to secure it.

Of greater concern was shoddy construction.