At the start of the war, the Confederacy enjoyed a crucial advantage in its officer corps. Three of the most important generals of the South—Robert E. Lee, James Longstreet, and "Stonewall" Jackson—were experienced and talented officers. On the Union side, President Lincoln began a frustrating search for capable military leaders through a process of trial and error.

Union officers were quickly replaced upon achieving bad results in battle, while the endless political maneuvering in Washington played an important part in many crucial promotions and demotions. After the Union's defeat at Bull Run on July 21, 1861, Lincoln replaced the commander of the Army of the Potomac, General Irvin McDowell, with General George B. McClellan, who would later be replaced by General Ambrose Burnside, who in turn was replaced by General Joseph Hooker. In the meantime, there was considerable grumbling among junior...