The Battle of Bunker Hill convinced the Continental Congress to establish an army for the defense of the colonies. They appointed forty-three-year-old George Washington as commander in chief, and he headed to Massachusetts to take command of militia companies already engaged in battle. Since the congress had not yet proclaimed itself a national government, Washington depended largely on the willingness of local militias to accept his command and of individual colonies to supply soldiers, arms, and ammunition. Throughout the summer of 1775, Washington wrote numerous letters to patriot political leaders detailing the army’s urgent need for men and supplies. He also sought to remove incompetent officers and improve order among the troops, who spent too much time carousing.

As he worked to forge a disciplined army, Washington and his officers developed a twofold military strategy. They sought to drive the British out of Boston and to secure the colonies from attack by British forces and their Indian allies in New York and Canada. In November 1775, American troops under General Richard Montgomery captured Montreal. However, the difficult trek in cold weather and the spread of smallpox decimated the patriot reinforcements led by General Benedict Arnold, and American troops failed to dislodge the British from Quebec.

Despite the disastrous outcome of the Canadian invasion, the Continental Army secured important victories in the winter of 1775–1776. To improve Washington’s position in Massachusetts, General Henry Knox retrieved weapons captured at Fort Ticonderoga. In March, Washington positioned the forty-three cannons on Dorchester Heights and surprised the British with a bombardment that drove them from Boston and forced them to retreat to Nova Scotia.