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.

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.

In November 1775, George Washington sent Henry Knox on a mission to bring the heavy artillery that had recently been captured at Fort Ticonderoga.

British commander William Howe saw his position as indefensible, and he withdrew his forces from Boston to Halifax, Nova Scotia on March 17.

The siege line was under the loose leadership of William Heath, who was superseded by General Artemas Ward late on April 20.

[12] General Gage wrote of his surprise at the number of Patriots surrounding the city: "The rebels are not the despicable rabble too many have supposed them to be....

[23] The siege did not blockade the harbor and the city remained open for the Royal Navy to bring in supplies from Nova Scotia and other places under Vice Admiral Samuel Graves.

[24] On May 3, the Massachusetts Provincial Congress authorized Benedict Arnold to raise forces for taking Fort Ticonderoga near the southern end of Lake Champlain in the Province of New York, which was known to have heavy weapons and only lightly defended.

On May 25, generals William Howe, John Burgoyne, and Henry Clinton arrived on HMS Cerberus, and Gage began planning to break out of the city.

In response, they sent instructions to General Ward to fortify Bunker Hill and the heights of Charlestown, and he ordered Colonel William Prescott to do so.

He set up his headquarters at the Benjamin Wadsworth House at Harvard College[35] and took command of the newly formed Continental Army the following day.

By this time, forces and supplies were arriving, including four independent companies of riflemen (not part of any state line) from Maryland and Virginia.

[44] On August 30, the British made a surprise breakout from Boston Neck, set fire to a tavern, and withdrew to their defenses.

[48] Washington summoned a council of war and made a case for an amphibious assault on Boston by sending troops across Back Bay in flat-bottomed boats which could hold 50 men each.

[49] In early September, Washington authorized the appropriation and outfitting of local fishing vessels for intelligence-gathering and interdiction of supplies to the British.

[51][52] On November 29, colonial Captain John Manley commanding the schooner Lee captured one of the most valuable prizes of the siege: the British brigantine Nancy just outside Boston Harbor.

Firewood was so scarce that British soldiers resorted to cutting down trees and tearing down wooden buildings, including the Old North Meeting House.

[57] Washington's army faced similar problems with smallpox, as soldiers from rural communities were exposed to the disease.

[59] In February, the water froze between Roxbury and Boston Common, and Washington thought that he would try an assault by rushing across the ice in spite of his shortage in powder; but his officers again advised against it.

He abandoned an attack across the ice with great reluctance in exchange for a more cautious plan of fortifying Dorchester Heights using cannon arrived from Fort Ticonderoga.

[60][61] British major general, Henry Clinton, and a small fleet set sail for the Carolinas in mid-January with 1,500 men.

Their objective was to join forces with additional troops arriving from Europe, and to take a port in the southern colonies for further military operations.

[63] Between November 1775 and February 1776, Colonel Henry Knox and a team of engineers used sledges to retrieve 60 tons of heavy artillery that had been captured at Fort Ticonderoga, bringing them across the frozen Hudson and Connecticut rivers in a difficult, complex operation.

[66] On March 5, Washington moved more of the Ticonderoga cannon and several thousand men overnight to occupy Dorchester Heights, overlooking Boston.

[74] On March 8, some prominent Bostonians sent a letter to Washington, stating that the British would not destroy the town if they were allowed to depart unmolested.

On March 9, the British saw movement on Nook's Hill in Dorchester and opened a massive artillery barrage that lasted all night.

[76] On March 10, 1776, General Howe issued a proclamation ordering the inhabitants of Boston to give up all linen and woolen goods that could be used by the colonists to continue the war.

He directed Captain Manley to harass the departing British fleet, in which he had some success, capturing the ship carrying Crean Brush and his plunder, among other prizes.