At the start of the Civil War he entered the Confederate Army as First Sergeant of Company C of the 20th Alabama Volunteers and fought in the Battles of Port Gibson, Baker's Creek and Vicksburg, where he was wounded and captured. After an exchange of prisoners, Tarrant rejoined his command and fought at Lookout Mountain and Missionary Ridge before joining General John Bell Hood's Tennessee Campaign which engaged Union troops in Franklin, Columbia and Nashville. From there he proceeded to Tupelo, Mississippi and finally to North Carolina. He was detached and sent home after the Battle of Bentonville and returned to farming.
In 1880 Tarrant was elected tax assessor for Jefferson County and was re-elected in 1884. In 1890 he was elected to assist Assessor S. L. Robertson for another six years. in 1900 he was elected to the Board of Revenue, which chose him president.
- Dubose, Joel Campbell (1904) Notable men of Alabama: Personal and Genealogical Vol. 1. Atlanta, Georgia: Southern Historical Association