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Historical ConflictBoston

Siege of Boston

The Siege of Boston was the opening phase of the American Revolutionary War, ending with the British evacuation of their first major stronghold.

Duration & Scope

1775 1776

1 year

Estimated Total Casualties

2K

Key Facts

Duration
~11 months (Apr 19, 1775 – Mar 17, 1776)
British casualties at Bunker Hill
~1,160
American casualties at Bunker Hill
~469
British evacuation destination
Halifax, Nova Scotia
Key artillery source
Fort Ticonderoga (cannon transported by Henry Knox)

Strategic Narrative Overview

After the costly British seizure of Bunker Hill and Breed's Hill in June 1775, which yielded heavy casualties on both sides without breaking the American encirclement, the siege settled into skirmishes, raids, and sniper fire. American forces on land and sea increasingly disrupted British supply lines. In January 1776, Henry Knox delivered artillery captured at Fort Ticonderoga, enabling Washington to fortify Dorchester Heights overlooking Boston harbor.

01 / The Origins

Following the first engagements of the American Revolutionary War at Lexington and Concord on April 19, 1775, Massachusetts militias moved quickly to block British land access to Boston. The Continental Congress convened in Philadelphia, formally established the Continental Army from these militias, and appointed George Washington as commander in chief, setting the stage for a prolonged siege of the British garrison holding the city.

03 / The Outcome

With cannon on Dorchester Heights threatening to sever the British naval supply line, General William Howe judged his position indefensible. On March 17, 1776, British forces evacuated Boston, sailing north to Halifax, Nova Scotia. The departure ended the siege, delivered Boston to American control, and marked the first significant strategic success for the Continental Army in the Revolutionary War.

Belligerents & Mobilization Analysis

Side A

1 belligerent

Continental Army / American Patriot Militia
Estimated Casualties469
Key Commanders

George Washington, Henry Knox.

Side B

1 belligerent

British Army (Garrison of Boston)
Estimated Casualties~1K
Key Commanders

William Howe.

Total Casualties (all sides)
1,629
Outcome
British evacuation of Boston to Halifax, Nova Scotia; city secured by Continental Army

Kinetic Engagement Axis

Major engagements timeline (1775–1776)Timeline of major military engagements plotted chronologically.177517761775Battles of Lexin…Allied1775Battle of Bunker…Side B1776Fortification of…Allied

Scroll horizontally to view full axis. Events plotted relatively.

Side A victorySide B victoryInconclusiveDecisive / turning point

Location

Map of Boston, United StatesMap of Boston, United StatesBoston, United States