At the outbreak of fighting in the American Revolution, Hull joined a local militia and was quickly promoted to captain, then to major, and to lieutenant colonel. He was in the battles of White Plains, Trenton, Princeton, Stillwater, Saratoga, Fort Stanwix, Monmouth, and Stony Point. He was recognized by George Washington and the Continental Congress for his service.

After the war, he moved to his wife's family estate in Newton, Massachusetts and served as a judge and state senator in Massachusetts. In 1805, President Thomas Jefferson appointed him governor of Michigan Territory. At the beginning of the War of 1812, Hull accepted a commission of brigadier general in command of the northwestern army, while also keeping his position as governor.

Hull was at least in part the victim of poor preparation for war by the U.S. government and mis-communication. While governor, Hull's repeated requests to build a naval fleet on Lake Erie to properly defend Detroit, Fort Mackinac, and Fort Dearborn were ignored. Hull began an invasion of Canada on July 12, 1812. However, he quickly withdrew to the American side of the river after hearing the news of the capture of Fort Mackinac by the British. He also faced unfreindly native american forces, which threatened to attack from the other direction.

Facing what he beleived to be superior forced, Hull surrendered Fort Detroit to Sir Isaac Brock on August 16, 1812. Accounts of the incident varied widely. A subordinate, Colonel Lewis Cass placed all blame for the surrender on Hull. After the war, Hull was court-martialed and sentenced to be shot, though upon reccommendation of mercy by the court, Hull received a reprieve from President James Madison.

Hull lived the remainder of his life in Newton, Massachusetts and wrote two books attempting to clear his name. Some later historians have agreed that Hull was unfairly made a scapegoat for the embarassing loss.