Battery E under the command of First Lieutenant Samuel Nicholl Benjamin fought at the Second Battle of Bull Run on 29–30 August 1862. Together with the 8th Massachusetts Light Artillery, Battery E was part of the division of Isaac Stevens in the IX Corps led by Jesse L. Reno. The unit also fought at the Battle of Chantilly on 1 September where Stevens was killed. It participated in the Maryland campaign on 6–22 September. At the Battle of Antietam on 17 September, Lieutenant Benjamin commanded four 20-pounder Parrott rifles. He recorded no casualties at Antietam and reported three officers and 97 enlisted men present for duty on 22 September. A return from 1 October listed three officers and 90 enlisted men. During the battle, the battery supported the attack on Burnside's Bridge. The battery remained on the east bank of Antietam Creek throughout the fighting. It was near Warrenton, Virginia on 15 November.