The fort played a significant part in the French and Indian War, and fell to the British in a nineteen-day siege in July 1759, called the Battle of Fort Niagara. The French relief force sent for the besieged garrison was ambushed at the Battle of La Belle-Famille, and the commander of the post, Pierre Pouchot, surrendered the fort to the British commander, Sir William Johnson, who initially led the New York Militia. The Irish-born Johnson was not the original commander of the expedition, but became its leader when General John Prideaux literally lost his head, stepping in front of a mortar being test-fired during the siege. The fort remained in British hands for the next thirty-seven years.