Commissioned into the
5th Regiment of Artillery upon graduation, Calef fought with it in the
Peninsula Campaign and at
Antietam. He transferred to
Battery A, 2nd U.S. Artillery and the
U.S. Horse Artillery Brigade in October 1862. While in command of Battery A during the early summer of 1863, his three-inch rifles supported Buford on the first day of the
Battle of Gettysburg. For his bravery during that battle and exemplary service during the war, Lieutenant Calef received brevet promotions to captain and major. Promoted to permanent
first lieutenant on November 3, 1863, Calef also acted as the regimental
adjutant of the
2nd Regiment of Artillery from November 1864 through March 1865. After the war, Lt. Calef remained in the
Regular Army. He was stationed for a considerable period at the
Presidio of San Francisco in California and at
Fort McHenry in
Baltimore, Maryland. He turned down an offer for a promotion to captain that would have required him to transfer branches to the 10th U.S. Cavalry. The 10th Cavalry was (along with the 9th) a regiment formed of African-American troopers. Though Calef's reasons for turning down the promotion can only be speculated, many officers at the time considered accepting command of black troops a career-ending move. Calef remained with the Artillery branch and earned his captaincy with the 2nd U.S. Artillery, and also briefly served as an instructor at the Artillery School of Practice at
Fort Monroe, in
Hampton, Virginia. He was promoted successively to command the
1st Regiment of Artillery as colonel of the regiment. ==Later life==