Gouverneur K. Warren
At the start of the war, Warren was a first lieutenant and mathematics instructor at the United States Military Academy at West Point, across the Hudson River from his hometown. He helped raise a local regiment for service in the Union Army and was appointed lieutenant colonel of the 5th New York Infantry on May 14, 1861. Warren and his regiment saw their first combat at the Battle of Big Bethel in Virginia on June 10, arguably the first major land engagement of the war. He was promoted to colonel and regimental commander on September 10.
In the 1862 Peninsula Campaign, Warren commanded his regiment at the Siege of Yorktown and also assisted the chief topographical engineer of the Army of the Potomac, Brig. Gen. Andrew A. Humphreys, by leading reconnaissance missions and drawing detailed maps of appropriate routes for the army in its advance up the Virginia Peninsula. He commanded a brigade (3rd Brigade, 2nd Division, V Corps) during the Seven Days Battles and was wounded in the knee at the Battle of Gaines' Mill, although he refused to be taken from the field. At the Battle of Malvern Hill, his brigade stopped the attack of a Confederate division. He continued to lead the brigade at the Second Battle of Bull Run, suffering heavy casualties in a heroic stand against an overwhelming enemy assault, and at Antietam, where V Corps was in reserve and saw no combat.
Commanders of the Army of the Potomac, Gouverneur K. Warren, William H. French, George G. Meade, Henry J. Hunt, Andrew A. Humphreys and George Sykes in September 1863.
Warren was promoted to brigadier general on September 26, 1862, and he and his brigade fought in the Battle of Fredericksburg in December. When Maj. Gen. Joseph Hooker reorganized the Army of the Potomac in February 1863, he named Warren his chief topographical engineer and then chief engineer. As chief engineer, Warren was commended for his service in the Battle of Chancellorsville.