In 2155, Travis Mayweather was part of the MACO unit aboard the ISS Enterprise (NX-01), with the rank of sergeant. When Commander Jonathan Archer mutinied against Captain Maximilian Forrest, Archer made Mayweather his personal guard. He promised to give Sergeant Mayweather better food, his own quarters, and several other privileges.
Archer had Mayweather severely beat alien workers found aboard the USS Defiant to learn who was responsible for the theft of key engineering components and the murder of a crewman. When Major Malcolm Reed was severely injured by the Gorn Slar, who was responsible for said thefts and killings, Mayweather assumed the duties of weapons officer. He also assisted Archer in murdering Admiral Black when he refused to promote Archer and grant him command of the Defiant on a permanent basis.
It turned out that Mayweather had been secretly plotting the takeover of the Defiant with Hoshi Sato after he became her consort. Mayweather helped Sato poison Archer, allowing her to take command of the Defiant and issue her ultimatum to Fleet Admiral Gardner.
In gratitude, Sato promoted Mayweather to captain, putting him in command of the Defiant, much to the resentment of his former superior Major Reed. In 2155, he was instrumental in rescuing Empress Sato from a rebel faction led by T'Pau and restoring her to power. (ENT: "In a Mirror, Darkly")