regiment in battle on June 16, 1862, during the Battle of Secessionville. The unit returned to the Union base at Newport News, Virginia, in July 1862, where it was assigned to the newly formed IX Corps. He was promoted to lieutenant colonel on July 1, 1861. He fought at the First Battle of Rappahannock Station on August 22 to August 25, 1862, in Culpeper County and Fauquier County, Virginia, and the Second Battle of Bull Run on August 28 to 30, 1862, in Prince William County, Virginia. His unit played a role in helping to stabilize the Union line at Fox's Gap during the Battle of South Mountain on September 14, 1862, near Boonsboro, Maryland. His unit came under friendly fire by the 9th New Hampshire Volunteer Infantry before reaching the line of combat, and his soldiers only saved themselves by throwing themselves down on the ground. Although the IX Corps participated in the Battle of Fredericksburg on December 11 to 15, 1862, in and around Fredericksburg, Virginia, Gerhardt's unit was held in reserve and he did not fight in the battle. His unit provided covering fire for crossings of the Rappahannock River early in the battle. He was promoted to colonel on December 17. He stayed with the unit when it went into winter quarters at Falmouth, Virginia. In mid-June 1863, the IX Corps was reassigned to the Army of the Tennessee. Gerhardt commanded the 46th New York Volunteers as it participated in the Siege of Vicksburg (then nearing its conclusion), and in the Jackson Expedition. The unit participated in the capture of Jackson, Mississippi, on July 17. The IX Corps was transferred to the Army of the Ohio in late July, and Gerhardt moved his troops to the army's headquarters at Knoxville, Tennessee. It participated in the Battle of Blue Springs on October 10, 1863, in Greene County, Tennessee. He was honorably mustered out of the volunteers due to an unspecified disability on November 8, 1863. A friend of President Lincoln's, Gerhardt again attended the Republican National Convention in 1864 as a Lincoln delegate. On July 23, 1866, Gerhardt was breveted to brigadier general effective March 13, 1865. Post-war career and death Gerhardt returned to live in the District of Columbia after the war, where he established a restaurant and remained active in local Republican Party politics as well as German community groups (such as the Washington Schuetzen