France became the first major ally of the United States during the Revolutionary War.
France formally allied with the United States through the Treaty of Alliance of 1778. The agreement followed the American victory at Saratoga in 1777, which convinced French leaders that the rebellion had a realistic chance of succeeding. France provided money, weapons, troops, naval forces, and diplomatic support against Britain.
French assistance was crucial to the American war effort. French troops and ships participated in the Yorktown campaign, where allied forces trapped Cornwallis's army and secured the decisive 1781 surrender. France's involvement also widened the conflict beyond North America and placed major pressure on Britain.
Spain later entered the war against Britain in 1779, but it did not sign the same formal alliance with the United States. France's relationship with the American revolutionaries began with covert aid before the 1778 treaties and continued through the final peace negotiations.