Dinwiddie, Robert (1693–1770), a British colonial administrator in America. He was governor (official title: lieutenant governor) of Virginia, 1751–58. His efforts, beginning in 1753, to prevent French encroachment on territory in the Ohio Valley claimed by Britain led to the French and Indian War. The war began in 1754 when militia under George Washington, sent by Dinwiddie to drive the French from Fort Duquesne (on the site of present-day Pittsburgh), were attacked and defeated by a larger French force at nearby Fort Necessity. During the war, Dinwiddie gathered supplies and recruited troops for the defense of Virginia's exposed frontier lands. He promoted intercolonial cooperation in the execution of the war, but these efforts were largely unsuccessful. Discouraged, he resigned and returned to England.