During what became known as the Battle of the Monongahela, British troops retreated in disarray but Washington rode back and forth across the battlefield, rallying the remnants of the British and Virginian forces to an organized retreat.

The French and their Indian allies ambushed the expedition, mowing down over 900 casualties including the mortally wounded Braddock. This was at the time the largest ever British military expedition ventured into the colonies, and was intended to expel the French from the Ohio Country. In 1755, Washington was the senior Colonial aide to British General Edward Braddock on the ill-fated Braddock Expedition. See also: Battle of Jumonville Glen, Battle of Fort Necessity, Braddock Expedition, and Forbes Expedition Braddock disaster 1755 Major-General Braddock's death at the Battle of the Monongahela, July 9, 1755. Both France and Britain responded by sending troops to North America in 1755, although war was not formally declared until 1756. These events had international consequences the French accused Washington of assassinating Jumonville, who they claimed was on a diplomatic mission similar to Washington's 1753 mission. The experience demonstrated Washington's bravery, initiative, inexperience and impetuosity. He was allowed to return with his troops to Virginia. The French responded by attacking and capturing Washington at Fort Necessity in July 1754. With Mingo allies led by Tanacharison, Washington and some of his militia unit ambushed a French scouting party of some 30 men, led by Joseph Coulon de Jumonville Jumonville was killed, and there are contradictory accounts of his death. Before he reached the area, a French force drove out the company's crew and began construction of Fort Duquesne. Governor Dinwiddie sent Washington back to the Ohio Country to protect an Ohio Company group building a fort at present-day Pittsburgh, Pennsylvania. Washington delivered the letter to the local French commander, who politely refused to leave. Washington also met with Tanacharison (also called 'Half-King') and other Iroquois leaders allied to Virginia at Logstown to secure their support in case of conflict with the French Washington and Half-King became friends and allies. Governor Dinwiddie received orders from the British government to warn the French of British claims, and sent Major Washington in late 1753 to deliver a letter informing the French of those claims and asking them to leave. The Ohio Company was one vehicle through which British investors planned to expand into the territory, opening new settlements and building trading posts for the Indian trade. These competing claims led to a world war 1756–63 (called the French and Indian War in the colonies and the Seven Years' War in Europe) and Washington was at the center of its beginning. In that year the French began expanding their military control into the ' Ohio Country', a territory also claimed by the British colonies of Virginia and Pennsylvania. Virginia's Royal Governor, Robert Dinwiddie, appointed Washington a major in the provincial militia in February 1753. Main article: George Washington in the French and Indian War

Washington appointed commander in chief