France became the United States’ formal military ally in 1778 during the American Revolutionary War.
The Franco-American Alliance was signed at Paris on February 6, 1778. The agreement recognized the United States as an independent nation and committed France to war against Britain. A separate treaty of amity and commerce was signed at the same time.
French support had already begun before the formal alliance. France supplied arms, ammunition, money, military equipment, and other assistance to the American rebels. Benjamin Franklin helped negotiate the treaties in Paris, where he served as a leading American diplomat.
French military and naval forces later played a crucial role. French troops fought alongside the Continental Army, and the French fleet helped prevent British reinforcement during the Yorktown campaign. The alliance therefore connected the political declaration of independence with the international struggle that secured it.