He rose to the rank of lieutenant general and served as Colonel Commandant of the Royal Marines, Portsmouth Division.
He was the officer commanding the ship's complement of Marines on board HMS Caesar during the Battle of Cape Ortegal in November 1805; the concluding action of the Trafalgar Campaign.
He first distinguished himself on shore while a Captain of Marines on HMS Hibernia, at the start of the Peninsular War.
During the War of 1812, he participated in the Chesapeake campaign, and was present at the battles of Bladensburg and Baltimore, and the attack on Washington.
Lewis became a brevet major and was appointed a Companion of the Order of the Bath, following his return to England in 1815.