France formally allied with the United States in 1778 during the American Revolution commemorated by America250.
The Franco-American Alliance was signed on February 6, 1778, after the American victory at Saratoga convinced French leaders that the rebellion had a realistic chance of success. The agreement included a treaty of alliance and a treaty of amity and commerce.
French aid extended far beyond diplomatic recognition. France supplied weapons, loans, soldiers, and naval forces. French troops and the fleet under Admiral de Grasse played a major role in trapping the British army at Yorktown in 1781.
Spain also fought Britain during the wider conflict, but Spain was not a formal ally under the same Franco-American treaty. France’s alliance was the pivotal foreign partnership of the American Revolution.