Ambrose Burnside, the son of a South Carolina slaveowner, was reared in Indiana, where his father had moved after freeing his slaves. At 19, Burnside was accepted an appointment to West Point. He would go on to graduate 18th in the class of 1847. He was brevetted 2nd Lieutenant, 2nd Artillery, and served in garrison duty during the Mexican War. Later, while stationed along the Southwest frontier, he received a slight wound during a skirmish with Apaches.
The easy-going officer got along well with people. He also had an attitude toward life that was almost cavalier. He liked to gamble, which sometimes resulted in poor judgment. In 1853, Burnside resigned his army commission to open a factory in Rhode Island to manufacture a breech-loading rifle of his own design. However, the enterprise depended on a government contract that the hapless businessman did not receive. He was forced into bankruptcy. Creditors who assumed control of the patents produced more than 55,000 "Burnside carbines" and millions of rounds of ammunition during the Civil War. Meanwhile, Burnside worked for his friend George B. McClellan, then chief engineer of the Illinois Central Railroad, survived being jilted at the altar by a Kentucky belle, and accepted an appointment as major general of the Rhode Island Militia.
When war erupted, Burnside rejoined the army as a colonel in the 1st Rhode Island Volunteers, a unit he had helped organize and one of the first 90-day regiments to reach Washington when the capital was threatened. He would later command a brigade at First Bull Run, and accept a promotion to brigadier general on August 6, 1861 from an admiring President Lincoln. Early in 1862, Burnside showed promise in coastal campaigns in North Carolina, destroying a small Confederate fleet in Albermarle and Palmico sounds. He also captured Roanoke Island, taking 2,600 prisoners and 32 guns, then proceeded to take New Berne, Beaufort, and Fort Macon, for which he was promoted to major general on March 18, 1862.
At Antietam, while under Maj. Gen. George B. McClellan, Burnside commanded the IX Corps and Maj. Gen. Joseph Hooker's I Corps. There, like his superior, he displayed signs of hesitancy when speed was critical to victory: as a result of Burnside's stubborn determination to cross a defended bridge over Antietam Creek–subsequently called "Burnside Bridge"–his arrival in the field was delayed, which cost him the opportunity to overrun the weak enemy positions opposite the site. His men would eventually cross the creek unopposed at a ford a mile downstream. However, the crossing was far too late to crush the Confederates on the other side.
Though he was an able subordinate, Burnside doubted his ability as a commander. Twice, after Lincoln became disillusioned with McClellan, he offered Burnside command of the Army of the Potomac, and twice Burnside declined the offer. Finally, on November 7, 1862, under orders from Washington, Burnside reluctantly accepted command. Aware of the necessity to exploit the Union victory at Antietam, Burnside decided to attack Robert E. Lee's army at Fredericksburg, Va., halfway between Washington and Richmond. As at Antietam, Burnside's irresolution and inability to see beyond his immediate objective, a heavily entrenched Confederate line along Marye's Heights, cost him the battle, as well as Lincoln's confidence. His defeat at Fredericksburg, in which the Union Army suffered 12,653 casualties to the South's 5,309, put a nearly irreversible dent in his army's morale. His attempt to cross the Rappahannock River in Jan. 1863 led to the disastrous "Mud March" and ultimately his removal from command.
In March, Burnside was given command of the Department of the Ohio. There, he presided over the arrest and military trial of Congressman Clement L. Vallandigham for alleged sedition, as well as captured Confederate cavalryman John Hunt Morgan and several of his men. That fall Burnside acquitted himself well by repulsing an assault on Knoxville by Confederate troops under Lt. Gen. James Longstreet.
In the spring of 1864, Burnside returned east to take command of his old IX Corps, leading it at the Wilderness, Spotsylvania, North Anna, Totopotomy, and Bethesda Church. Finally, at Petersburg, Burnside's failure once again to move quickly resulted in the slaughter of his men at the Battle of the Crater. He was relieved of his command for improper handling of troops, resigning his commission on April 15, 1865.
After the war, Burnside was elected governor of Rhode Island three times, in 1866, 1867, and 1868, and returned to his business activities. In 1874, he was elected a position on the U.S. Senate, serving there until his death on September 13, 1881.