During the period when Simon Girty lived with them (1756–1764), Guyasuta and the Ohio Seneca fought in many battles against the British in the French and Indian War. Guyasuta was instrumental in defeat of Major James Grant at the Battle of Fort Duquesne on September 14, 1758. The French and Indian War officially ended in 1763, but hostilities between the Indians and the British continued in Pontiac's War. Guyasuta and the Ohio Seneca were allied with Pontiac, and fought the British alongside his warriors at the July 1763 Siege of Fort Pitt, the July 31, 1763 Battle of Bloody Run, the August 5–6, 1763 Battle of Bushy Run, and the September 14, 1763 Devil's Hole Massacre (the deadliest engagement for British soldiers during the war). It's unclear if Simon Girty fought along with Guyasuta in this war.