In 1755, George Washington accompanied British General Braddock's expedition. Two regiments marched from Fort Cumberland across the Allegheny Mountains and into western Pennsylvania. Following a path Washington surveyed, over 3,000 men built a wagon road wide, that when complete, was the first road to cross the Appalachian Mountains. Braddock's Road, as it was known, blazed the way for the future National Road (US40). The expedition crossed the Monongahela River on July 9, 1755. French troops from Fort Duquesne ambushed Braddock's expedition at Braddock's Field, nine miles (14 km) from Fort Duquesne. In the Battle of the Monongahela, the French inflicted heavy losses on the British, and Braddock was mortally wounded. The surviving British and colonial forces retreated. This left the French and their Native American allies with dominion over the upper Ohio valley.