In the first battle in which Jackson took part, the confused struggle at Bull Run, he gained his name of Stonewall from the firmness with which he kept his men to their work and repulsed the attack of the Union troops. From that time until his death, less than two years afterward, his career was one of brilliant and almost uninterrupted success; whether serving with an independent command in the Valley, or acting under Lee as his right arm in the pitched battles with McClellan, Pope, and Burnside. Few generals as great as Lee have ever had as great a lieutenant as Jackson. He was a master of strategy and tactics, fearless of responsibility, able to instil into his men. his own intense ardor in battle, and so quick in his movements, so ready to march as well as fight, that his troops were known to the rest of the army as the "foot cavalry."

In the spring of 1863 Hooker had command of the Army of the Potomac. Like McClellan, he was able to perfect the discipline of his forces and to organize them, and as a division commander he was better than McClellan, but he failed even more signally when given a great independent command. He had under him 120,000 men when, toward the end of April, he prepared to attack Lee's army, which was but half as strong.