In 1755, Washington was the senior Colonial aide to British General Edward Braddock on the ill-fated Braddock Expedition. 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. The French and their Indian allies ambushed the expedition, mowing down over 900 casualties including the mortally wounded Braddock. 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.