American Revolution in Massachusetts

Washington at Dorchester Heights, Emanuel Leutze (1852)

Some of the armaments were used to fire on Boston from Cambridge and Roxbury in order to distract the British forces while preparations for the fortification of Dorchester Heights were underway. Dorchester Heights was finally fortified during the night of March 4 into March 5, led by Brigadier General John Thomas with a force of 800 soldiers and 1,200 workers. The construction noises were hidden by the noise of further bombardments.

General Howe, upon being made aware of the fortifications, first launched a failed barrage of cannon fire against the heights.  He then planned an assault on Dorchester Heights. Washington had already planned and prepared countermeasures to an assault, and increased the number of soldiers on the Dorchester line to nearly 6,000.  

A snowstorm that developed late in the day on March 5th lasted for several days and delayed Howe’s planned assault. By the time the storm was over Howe had reconsidered, deciding that it would be better to save his forces for other battles rather than deplete them trying to hold Boston. A unsigned letter was sent to Washington's position on March 8, saying that Boston would not be destroyed so long as the British were allowed to leave without interference. Although Washington did not formally acknowledge the letter, he did allow the British to leave Boston unmolested.