Which 1778 treaty formally created the Franco-American alliance during the Revolution?

The Treaty of Alliance formally created the Franco-American alliance in 1778.

The United States and France signed the treaty on February 6, 1778, alongside the Treaty of Amity and Commerce. France agreed to support the United States against Great Britain, and the two countries promised not to make a separate peace during the conflict.

French assistance followed the American victory at Saratoga in 1777, which convinced France that the rebellion could succeed. France supplied money, weapons, troops, and naval power. French intervention expanded the conflict into a global war involving Britain and several European powers.

The alliance was decisive at Yorktown in 1781, where French naval forces helped prevent a British evacuation or reinforcement by sea while French and American armies surrounded General Cornwallis. The alliance remained legally important until the United States effectively ended it through the 1798 Treaty of Mortefontaine.