France formally allied with the United States after the American victory at Saratoga, turning the Revolutionary War into a wider international conflict.
The Battles of Saratoga took place in September and October 1777 in northern New York. American forces compelled British general John Burgoyne to surrender his army on October 17. The victory convinced France that the American cause had a realistic chance of defeating Britain.
The two countries signed the Treaty of Amity and Commerce and the Treaty of Alliance in February 1778. France supplied weapons, money, soldiers, ships, and naval support. French involvement forced Britain to divide its military resources among North America, the Caribbean, Europe, and other theaters.
French assistance was crucial at Yorktown in 1781, where a French fleet blocked British reinforcement by sea while French and American troops surrounded the British army. Spain and the Dutch Republic also opposed Britain, but France was the first major European power to establish a formal alliance with the United States.