During the Revolutionary War, Lieutenant General Wilhelm von Knyphausen and a force of 3,000 Hessian mercenaries lay siege to Fort Washington on Long Island. Throughout the morning, Knyphausen met stiff resistance from the Patriot riflemen inside, but by the afternoon the Americans were overwhelmed, and the garrison commander, Colonel Robert Magaw, surrendered. Three thousand Americans were taken prisoner, and valuable ammunition and supplies were lost to the Hessians.
Two weeks earlier, William Demont had deserted from the Fifth Pennsylvania Battalion and given British intelligence agents information about the Patriot defense of New York, including information about the location and defense of Fort Washington. Demont was the first traitor to the Patriot cause, and his treason contributed significantly to Knyphausen's victory.