One major factor was when the French finally decided to help the colonists. They sent a army on land and their navy at sea. So while both the colonist (Americans) and French blocked the British on land, the French navy ultimately prevented the British from using their sea escape route. With no strategic options left, General Cornwallis, the British general of the Battalion surrendered. This victory wasn't just a battle victory for the colonist, it was what allowed them to win the war.