The fortification of Dorchester Heights by the Continental Army made Boston untenable for the British: Henry Knox’s cannon dominated the city and the harbor. On 5 March 1776, Gen Howe prepared 2500 redcoats to seize the Rebel position just as he had done ten months before at Bunker Hill. The operation would commence at dawn the next day.
General George Washington expected the attack and placed 6000 troops on Dorchester Heights to repel it. But he also knew that if the British managed to close and come at his poorly trained and poorly disciplined troops with the bayonet, no amount of continentals would matter – they would break. Even a Pyrrhic victory for the British like Bunker Hill would spell the end of the siege of Boston. Washington’s critical shortage of powder would be exposed to all the world, and without the cannon the British navy could supply Howe indefinitely. That would leave Washington just one remaining option: Storm the city.
Washington couldn’t chance a loss of the Dorchester Heights without possession of Boston – It would be the end of the Revolution. And he couldn’t storm the city while the navy was in the harbor… Unless it was distracted.
Which it would be supporting Howe’s assault.
Washington decided to gamble everything on a single throw of the dice. While Howe and his best troops were busy south of the city supported by the British Navy, Washington’s best regiments would assault over the Boston Neck, overwhelm the redoubt with sheer numbers, and seize the city. The casualties would be excessive, but a loss at Dorchester would be fatal to the Revolution if he didn’t already have Boston. He would lead the attack the moment Howe’s men were committed on the peninsula and unable to reinforce the Boston neck.
On the night of 5/6 March 1776, Rebel spies reported British assault troops were loading flatboats for transport across the harbor. Washington brought up his best regiments, including the fishermen from Marblehead that proved so critical in the year ahead, to assault positions before the neck. The morning of 6 March was expected to be the bloodiest of the war.
But it wasn’t to be: A fierce and blinding, but unexpected, snowstorm hit Boston around midnight and continued throughout the morning. About noon it stopped as quickly as it started. But by then Howe couldn’t attack. His flatboats would be easy targets for Knox’s guns. He knew surprise was lost and Washington would reinforce the heights. Losing a large part of his army in another Bunker Hill just to be bottled up on another peninsula would gain him nothing. (Remember he didn’t know about the shortage of powder.) The next day Howe drafted a note to Washington offering not to burn Boston to the ground if he was allowed to evacuate unmolested.
Washington quickly agreed. On 17 March as the last Redcoat and loyalist were boarding ships in the harbor, Washington triumphantly entered Boston. As he was traversing the Boston Neck, he eyed the British redoubts and fortifications he planned to personally assault on the morning of 6 March 1776.
No amount of troops could have forced the Neck: The Americans would have been massacred, and Washington would have undoubtedly been killed leading the charge. It wasn’t the last time Washington and the Continental Army was saved by the weather.