Born in Boston in 1793, Sumner joined the Army in 1819. He had already spent more than a quarter of a century in the military when he fought in the Mexican War (1846-48), traveling down the Santa Fe Trail with Stephen Watts Kearney to capture New Mexico. Sumner was transferred to Winfield Scott’s command for the remainder of the war, and earned the nickname “Bullhead” when a bullet ricocheted off his skull at the Battle of Cerro Gordo.
Sumner served in Kansas during the 1850s when pro-slave and anti-slave settlers there clashed. He provided escort for president-elect Abraham Lincoln in 1861, and when the Civil War erupted, Lincoln made Sumner commander of the Department of the Pacific. In March 1862, he was given command of II Corps in the Army of the Potomac. During the Seven Days’ Battles in June, Sumner performed somewhat sluggishly but his fighting spirit carried down to his men. At Antietam in September, Sumner’s men attacked General Thomas J. “Stonewall” Jackson’s corps and nearly broke it before heavy fire drove them back. Sumner’s command suffered aheavy toll, absorbing nearly half of the Union’s 12,500 casualties from that day.
Sumner fought at Fredericksburg, Virginia,in December 1862, and remained loyal to General Ambrose Burnside in early 1863 when several generals were contemplating a mutiny against their commander. Tired of the infighting and political intrigue among the Army of the Potomac’s staff, and perhaps feeling too old to command in the field, Sumner requested reassignment. He was again appointed to the Department of the Pacific, but died in Syracuse, New York, on March 21, 1863, before moving to the West.