Siege of Boston

The siege of Boston (April 19, 1775 – March 17, 1776) was the opening phase of the American Revolutionary War. In the siege, American patriot militia led by newly-installed Continental Army commander George Washington prevented the British Army, which was garrisoned in Boston, from moving by land. Both sides faced resource, supply, and personnel challenges during the siege. British resupply and reinforcement was limited to sea access, which was impeded by American vessels. The British ultimately abandoned Boston after eleven months, moving their troops and equipment north, to Nova Scotia.

The siege began on April 19 after the Revolutionary War's first battles at Lexington and Concord, when Massachusetts militias blocked land access to Boston. The Continental Congress, meeting in Philadelphia, formed the Continental Army from the militias involved in the fighting and appointed George Washington as commander in chief. In June 1775, the British seized Bunker Hill and Breed's Hill, which Washington and the Continental Army was preparing to bombard, but their casualties were heavy and their gains insufficient to break the Continental Army's control over land to Boston. After this, the Americans laid siege to Boston; no major battles were fought during this time, and the conflict was limited to occasional raids, minor skirmishes, and sniper fire. British efforts to supply their troops were significantly impeded by the smaller but more agile Continental Army and patriot forces that were operating on land and sea. The British suffered from a continual lack of food, fuel, and supplies.

In November 1775, George Washington sent Henry Knox on a mission to bring the heavy artillery that had recently been captured at Fort Ticonderoga. In a technically complex and demanding operation, Knox brought the cannons to Boston in January 1776, and this artillery fortified Dorchester Heights which overlooked Boston harbor. This development threatened to cut off the British supply lifeline from the sea. British commander William Howe saw his position as indefensible, and he withdrew his forces from Boston to Halifax, Nova Scotia on March 17.