A West Point graduate (1844), he served with distinction in the Mexican War (1846–48). Hancock was appointed a brigadier general of volunteers on the outbreak of the Civil War and served in the Peninsular campaign of 1862. In May 1863 he was made head of the II Corps, Army of the Potomac, which he led for most of the remaining two years of the war. He served with distinction at the Battle of Gettysburg (July 1863) and participated in the drive on Richmond, Va., the following spring. As a major general after the war, he commanded (1866–68) various army departments, including the military division composed of Louisiana and Texas. Although great discretionary power had been conferred upon him, Hancock insisted on the maintenance of the civil authorities in their “natural and rightful dominion.” This stand enraged some Republicans, who were counting on military power to protect black and white Republicans in the South, but his policy won him the support of the Democrats, who nominated him for the presidency in 1880. After narrowly losing the election to the Republican candidate, James A. Garfield, he returned to military life.