The fort is situated at a very strategic point at the southern tip of Lake Champlain, and had been in British hands since the Peace of Paris in 1763. At the time of the attack it was neither well-maintained nor well-guarded; furthermore the garrison had no idea that hostilities had broken out in Concord and Lexington.

Ethan Allen recognized the significance of capturing the fort and was preparing to do so, with the Green Mountain Boys, when Benedict Arnold arrived with a military commission from the Massachusetts and Connecticut revolutionary councils to lead an attack.

The Green Mountain Boys refused to serve under anyone other than their own commander, so Ethan took charge leaving Benedict Arnold the honor of being co-commander of the force. At dawn on May 10th the fort was easily taken, as the garrison of a mere fifty men was indeed totally surprised.

Crown Point, another British fort a few miles to the north, was also taken without an engagement the following day. The capture of these two forts secured protection from the British to the north, and provided much needed cannon for the colonial army.