Final answer:
France decided to support the Patriots after the Battle of Saratoga, providing them with military support and assistance.
Step-by-step explanation:
After the Battle of Saratoga, the nation that decided to support the Patriots was France. The American victory at Saratoga convinced the French to recognize American independence and form a military alliance with the new nation. The French provided the United States with gunpowder, money, soldiers, and naval forces that played a crucial role in defeating Great Britain.