The Siege of Boston was a key event during the early stages of the American Revolutionary War. It began in April 1775 when colonial militias surrounded the city, which was held by British troops. The siege aimed to cut off supplies and reinforcements to the British forces, who were stationed in Boston. The siege lasted until March 1776, culminating in the Battle of Dorchester Heights. American forces, led by George Washington, successfully positioned artillery on high ground, forcing the British to evacuate. This marked a significant turning point in the war, boosting colonial morale and solidifying Washington's leadership.