Civil War service First commissions and Bull Run thumb|alt=A black-and-white photograph of a man seated with his left hand inside of his jacket. His body faces the right diagonal and his head faces left.|Mathew Brady photographed Sherman, . Sherman was first commissioned as colonel of the 13th U.S. Infantry Regiment, effective May 14, 1861. This was a new regiment yet to be raised. In fact, Sherman's first command was a brigade of three-month volunteers who fought in the First Battle of Bull Run on July 21, 1861. It was one of the four brigades in the division commanded by General Daniel Tyler, which was in turn one of the five divisions in the Army of Northeastern Virginia under General Irvin McDowell.
Civil War service First commissions and Bull Run thumb|alt=A black-and-white photograph of a man seated with his left hand inside of his jacket His body faces the right diagonal and his head faces left.|Mathew Brady photographed Sherman, . Sherman was first commissioned as colonel of the 13th U.S. Infantry Regiment, effective May 14, 1861. This was a new regiment yet to be raised. In fact, Sherman's first command was a brigade of three-month volunteers who fought in the First Battle of Bull Run on July 21, 1861. It was one of the four brigades in the division commanded by General Daniel Tyler, which was in turn one of the five divisions in the Army of Northeastern Virginia under General Irvin McDowell.