Which 1777 American Revolutionary War victory persuaded France to openly ally with the United States?

The Battles of Saratoga in 1777 persuaded France to openly ally with the United States.

Saratoga was a campaign in upstate New York consisting chiefly of the Battle of Freeman’s Farm on September 19 and the Battle of Bemis Heights on October 7. British Lieutenant General John Burgoyne’s army was eventually surrounded and surrendered on October 17.

The American victory demonstrated that the Continental forces could defeat a major British army. France had already been secretly supplying the American cause, but Saratoga changed its assessment of the war. In 1778, France formally entered the conflict on the American side through the Treaty of Alliance.

People often refer to “the Battle of Saratoga” as though it were one engagement. In fact, the name commonly covers the two main battles and the surrounding campaign. The later American victory at Yorktown in 1781 ended major fighting, but Saratoga was the military success that brought France into the war openly.