Initially, France remained reluctant to directly involve themselves in the war against Great Britain. In part, they worried that revolutionary fervor might spread into their own empire (which it did by 1789), but they also did not think the American colonists could win. However, the October 1777 surrender of British General John Burgoyne's army at Saratoga won for Americans the assistance they needed from other foreign powers. France and the United States subsequently signed a treaty on February 6, 1778, creating a military alliance between the two countries. In response, Great Britain declared war on France five weeks later, on March 17.