Ambrose Burnside in the context of Governor of Rhode Island

Sideburns, sideboards, or side whiskers are facial hair grown on the sides of the face, extending from the hairline to run parallel to or beyond the ears. The term sideburns is a 19th-century corruption of the original burnsides, named after American Civil War general Ambrose Burnside, a man known for his unusual facial hairstyle that connected thick sideburns by way of a moustache, but left the chin clean-shaven.

The eastern theater of the American Civil War consisted of the major military and naval operations in the states of Virginia, West Virginia, Maryland, and Pennsylvania, the national capital in Washington, D.C., and the coastal fortifications and seaports of North Carolina. The interior of the Carolinas were considered part of the western theater, and other coastal areas along the Atlantic Ocean were part of the lower seaboard theater.

The eastern theater was the venue for several major campaigns launched by the Union Army of the Potomac to capture the Confederate capital of Richmond, Virginia; many of these were frustrated by the Army of Northern Virginia, a division of the Confederate States Army, commanded by General Robert E. Lee. President Abraham Lincoln responded by seeking a general to match Lee's boldness, and successively appointed Major General Irvin McDowell, George B. McClellan, John Pope, Ambrose Burnside, Joseph Hooker, and George G. Meade to command his principal eastern armies.

The Battle of Fort Sanders was the crucial engagement of the Knoxville Campaign of the American Civil War, fought in Knoxville, Tennessee, on November 29, 1863. Assaults by Confederate Lt. Gen. James Longstreet failed to break through the defensive lines of Union Maj. Gen. Ambrose Burnside, resulting in lopsided casualties, and the Siege of Knoxville entered its final days.

The Battle of Fredericksburg was fought December 11–15, 1862, in and around Fredericksburg, Virginia, in the Eastern Theater of the American Civil War. The combat between the Union Army of the Potomac commanded by Maj. Gen. Ambrose Burnside and the Confederate Army of Northern Virginia under Gen. Robert E. Lee included futile frontal attacks by the Union army on December 13 against entrenched Confederate lines, hurling themselves against a feature of the battlefield that came to be remembered as the 'sunken wall' on the heights overlooking the city. It is remembered as one of the most one-sided battles of the war, with Union casualties more than twice as heavy as those suffered by the Confederates. A visitor to the battlefield described the battle as a "butchery" to U.S. President Abraham Lincoln.

Burnside planned to cross the Rappahannock River at Fredericksburg in mid-November and race to the Confederate capital of Richmond before Lee's army could stop him. Burnside needed to receive the necessary pontoon bridges in time, and Lee moved his army to block the crossings. When the Union army was finally able to build its bridges and cross under fire, direct combat within the city resulted on December 11–12. Union troops prepared to assault Confederate defensive positions south of the city and on a strongly fortified ridge just west of the city known as Marye's Heights.