The major event in the Boston area in the first year of the American Revolution was the Siege of Boston from 19 April 1775 to 17 March 1776. The Continental Army under George Washington besieged British forces in the city. The British built several forts as a result, notably on Governor's Island and Noddle's Island. In January 1776 artillery captured at Fort Ticonderoga in upstate New York was brought to the Boston area under Henry Knox, providing the Patriot forces with more and larger cannon than they previously had. In the first week of March these weapons were used to engage the enemy. The turning point was the capture and fortification of Dorchester Heights on 5 March, allowing the Continental Army to bombard the British fleet in the harbor. The British evacuated Boston on 17 March under a truce, taking the ships carrying their army to Halifax, Nova Scotia. However, they damaged and destroyed Castle William and its ordnance as best they could, to deny its use to the Patriots.