The Franco-American alliance was the 1778 alliance between the Kingdom of France and the United States during the American Revolutionary War. Formalized in the 1778 Treaty of Alliance, it was a military pact in which the French provided many supplies for the Americans. The Netherlands and Spain later joined as allies of France; Britain had no European allies. The French alliance was possible once the Americans captured a British invasion army at Saratoga in October 1777, demonstrating the viability of the American cause.