On 2 and 3 March 1776, Henry Knox’s cannon from Ft Ticonderoga opened fire on British positions around Boston. They did the same on the late afternoon of 4 March. But as the British were safely tucked away riding out Knox’s bombardment, LTG George Washington put in motion his plan to fortify Dorchester Heights, which overlooked Boston and the harbor.

As soon as the sun sank below the horizon, thousands of Continentals trudged up the heights with hay bales. With these they created a wall in the darkness that obscured their movements and muffled the sound of thousands of soldiers digging. Then they dug trenches and gun pits for cannon throughout the night. By 4am, the last of Knox’s guns were in place. The hay bale wall was dismantled and the bales were used to reinforce the position. The guns on Dorchester Heights dominated Boston Harbor. Admiral Shuldham informed Gen Howe, the commander of the British army in Boston, that the city was untenable. The stunned Howe replied, “The rebels have done more in one night than my whole army would have done in a month.”

But it was all a bluff: Washington barely had enough powder to hold the heights if the British attacked as they did at Breed’s Hill, much less clear the British Navy from the harbor.