Perched on Manhattan schist at the island’s highest point and paired with Fort Lee across the Hudson, Fort Washington looked impregnable in the autumn of 1776. This deep dive explores how that confidence became the Continental Army’s most disastrous defeat of the American Revolution. The rocky ground left no soil for trenches, early wins against British frigates and Hessian troops inflated egos, and Washington let Nathanael Greene and Colonel Robert Magaw keep nearly 3,000 men in a fort built for about 1,000.

Then adjutant William Demont deserted and handed the fort’s plans to General William Howe. On November 16, Howe launched a multi-pronged assault with a Highlander feint that pulled the southern defenders apart, while a shifting Harlem River tide delayed the Hessians. Rifles jammed, defenders hurled boulders, Margaret Corbin manned her fallen husband’s cannon, and 2,837 Americans were captured, most of whom died on British prison ships.

• Why the fort’s rocky foundation was a hidden weakness
• Washington’s doubts and the officers who overruled his instinct
• William Demont’s betrayal and General Howe’s battle plan
• Margaret Corbin and the desperate defense of the northern slope
• How the disaster set the stage for Trenton and Princeton