The most important French fort planned was intended to occupy a position at "the Forks" where the Allegheny and Monongahela Rivers meet to form the Ohio River (present-day Pittsburgh, Pennsylvania). Peaceful British attempts to halt this fort construction were unsuccessful, and the French proceeded to build the fort they named Fort Duquesne. British colonial militia from Virginia were then sent to drive them out. Led by George Washington, they ambushed a small French force at Jumonville Glen on 28 May 1754 killing ten, including commander Jumonville. The French retaliated by attacking Washington's army at Fort Necessity on 3 July 1754 and forced Washington to surrender. These were the first engagements of what would become the worldwide Seven Years' War.