Burgoyne's strategy to divide New England from the southern colonies had started well but slowed due to logistical problems. He won a small tactical victory over General Horatio Gates and the Continental Army in the September 19 at the cost of significant casualties. His gains were erased when he again attacked the Americans in the October 7 and the Americans captured a portion of the British defenses. Burgoyne was therefore compelled to retreat, and his army was surrounded by the much larger American force at Saratoga, forcing him to surrender on October 17. News of Burgoyne's surrender was instrumental in formally bringing France into the war as an American ally, although it had previously given supplies, ammunition, and guns, notably the de Valliere cannon which played an important role in Saratoga.