Today in history, on March 17, 1776, British forces evacuated Boston after George Washington and Henry Knox set up artillery on Dorchester Heights, overlooking the city. The event was the culmination of one of the most incredible feats of the war.
The British evacuation from Boston relied upon a truly daring plan to bring artillery from Fort Ticonderoga to Boston. Concocted by Henry Knox, a brilliant young colonel in the Continental Army, the idea defied conventional time constraints and logistical expectations. Over the course of three winter months, 60 tons of cannons were moved by boat, horse, and ox-drawn sledges. Artillery was carried over swamps, dense forests, and rivers, some of which were partially frozen.
Prior to the Continental siege of Boston, both British and patriot forces understood the importance of Dorchester Heights. Positioning the Continental Army in the area around Boston, Washington briefly considered taking the heights but reneged when it became clear the army was not ready to suffer a British attack on the position. British General William Howe’s early attempt to take the high ground had led to the Battle of Bunker Hill, a pyrrhic British victory.
When Knox’s cannons arrived, Washington hastily made use of them despite complications brought about by the frozen ground. Meanwhile, General John Thomas brought 2,000 troops to Dorchester Heights to begin the construction of fortifications. From March 2-5, cannon bombardments continued as Thomas fortified the heights.
After observing the siege, British Admiral Molyneux Shuldham declared that the British fleet would be in danger unless the heights were taken by the British army. Howe made plans for an assault, but Washington was made aware of it and responded by reinforcing the line to 6,000 men. After a snow storm disrupted a potential clash of the armies, British forces retreated to Halifax, Nova Scotia, bringing 1,000 loyalists with them as well. Howe lamented that “the rebels have done more in one night than my whole army could do in months.”
A spectacular achievement, the siege of Boston is often considered one of the most significant events of the entire war. According to historian Murray Rothbard, Knox had devised and executed a “fantastically ambitious plan,” and “a feat at which soldiers and engineers still marvel.” Knox’s deed earned him standing in the Continental Army, and he was promoted to brigadier general later that year.
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