He was made
captain in 1843, and was on frontier duty in
Indian Territory and
Arkansas until 1846. He served in the
Mexican–American War in 1847, taking part in the
Siege of Veracruz and the battles of
Cerro Gordo and Amazoque. Todd was on garrison and frontier duty till 1855, when he was engaged in the action of Blue Water against the
Sioux Indians. He resigned from the
United States Army on September 16, 1856, and became an Indian trader, settling at
Fort Randall, Dakota Territory. He was admitted to the bar in 1861 and commenced the practice of law in
Yankton. With the outbreak of the Civil War, he was appointed on September 19, 1861, as a
brigadier general of Volunteers. He was in command of the North Missouri district from October 15 until December 1, 1861. He resigned from the Army on July 17, 1862. ==Dakota Territory==