Which French treaty formally made France an ally of the American revolutionaries in 1778?

The Treaty of Alliance formally made France an ally of the American revolutionaries in 1778.

France signed the treaty with the United States on February 6, 1778, alongside the Treaty of Amity and Commerce. The alliance promised military cooperation if Britain attacked French ships or territories and required the United States to avoid making a separate peace with Britain without French consent. France thereby moved from covert assistance to open participation in the American Revolutionary War.

The American victory at Saratoga in October 1777 helped persuade France that the rebellion could succeed. French financial aid, weapons, troops, and naval forces became crucial. French support contributed directly to the American victory at Yorktown in 1781, where a French fleet helped prevent British evacuation by sea.

The treaty is sometimes called the Franco-American Alliance. It should not be confused with the Treaty of Paris of 1783, which ended the war and recognized American independence. The alliance also shaped early American diplomacy and remained formally relevant until the United States ended it through the Treaty of Mortefontaine in 1800.