SUMMARY Ambrose E. Burnside was a major general in the Union army during the American Civil War (1861–1865). Instantly recognizable for his bushy sideburns (the term itself is derived from reversing his last name), Burnside was one of four men to command the Army of the Potomac in Virginia. Offered the job twice previously—following George B. McClellan‘s failed Peninsula Campaign in 1862 and following the Second Battle of Manassas later that summer—he turned it down, citing his own lack of experience and encouraging his peers and, subsequently, historians to question his self-confidence. When he did take command of the army, he led it into disaster at the Battle of Fredericksburg (1862), perhaps the Union’s most lopsided defeat of the war. After his corps was badly defeated at the Battle of the Crater (1864) he went home on a leave of absence from which he was never called back to duty. Burnside’s dismal reputation is probably unfair, however. He was an innovative engineer but an unlucky general who was often made a scapegoat for larger failures.