Which 1777 American Revolution victory persuaded France to become an open American ally?

The Battles of Saratoga in 1777 persuaded France to become an open American ally during the American Revolution.

The campaign consisted mainly of two major battles near Saratoga, New York: the first on September 19 and the second on October 7. American forces under General Horatio Gates eventually forced the British army commanded by General John Burgoyne to surrender on October 17.

Saratoga mattered beyond the battlefield. The American victory showed France that the rebellion had a realistic chance of success, encouraging the Franco-American Alliance of 1778. French military aid, money, supplies, and naval power later played a major role in the struggle against Britain.

The name can cause confusion because “Saratoga” refers both to the overall campaign and to its two principal battles. The victory is widely described as a turning point, but the war continued for several more years before Britain recognized American independence.