In April 1754, Washington was on his way to establish a post at the Forks of the Ohio, but then he learned that the French had already built a fort there. Warned that the French were advancing, he quickly threw up fortifications at Great Meadows naming the entrenchment Fort Necessity, and marched to intercept advancing French troops. After a brief fight, Washington pulled his small force back into Fort Necessity, where the French overwhelmed him. Surrounded by enemy troops, with his food supply almost exhausted and his dampened ammunition useless, Washington capitulated. Under the terms of the surrender signed that day, he was permitted to march his troops back to Williamsburg.
Discouraged by his defeat and angered by discrimination between British and colonial officers in rank and pay, he resigned his commission near the end of 1754. The next year he volunteered to join British general Edward Braddock's expedition against the French. When the French and their Indian allies ambushed Braddock on the Monongahela River, Washington tried to rally the Virginia troops. At the age of 23, Washington was promoted to colonel and appointed commander in chief of the Virginia militia, with responsibility for defending the frontier.
Washington left the army in 1758 and returned to Mount Vernon and directed his attention toward his neglected estate. He entered politics serving in Virginia's House of Burgesses. In January 1759 he married Martha Dandridge Custis, a wealthy and attractive young widow with two small children. Washington became a leader in Virginia's opposition to Great Britain's colonial policies. In June 1775 he was Congress's unanimous choice as commander in chief of the Continental forces.
Washington took command of the troops surrounding British occupied Boston on July 3, devoting the next few months to training the undisciplined 14,000 man army and trying to secure urgently needed powder and other supplies.