The Franco-American alliance refers to 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 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. The alliance became controversial after 1793 when Britain and Revolutionary France again went to war and the U.S. declared itself neutral. Relations between France and the United States worsened as the latter became closer to Britain in the Jay Treaty of 1795, leading to an undeclared Quasi War. The alliance was defunct by 1794 and formally ended in 1800.