In 1755, John Butler was appointed to the rank of captain in the Indian Department of the British colonial government. He served in the French and Indian War under Sir William Johnson. In 1758, he saw action with James Abercromby at Fort Ticonderoga and John Bradstreet at the Battle of Fort Frontenac. In 1759, he was made second in command of the Indians with Johnson at the Battle of Fort Niagara. In 1760, he continued as a second in command of the Indians in Jeffery Amherst's force at Montreal.