American Military History, Volume 1 by Richard W. Stewart

While a small Confederate garrison at Yorktown made ready to delay McClellan, Johnston hurried his army to the peninsula. In Richmond, Confederate authorities had determined on a spectacularly bold diversion. Robert E. Lee, who had moved rapidly to the rank of full general, had assumed the position of military adviser to Confederate President Jefferson Davis on March 13. Charged with the conduct of operations of the Confederate armies under Davis' direction, Lee saw that any threat to Washington would cause progressive weakening of McClellan's advance against Richmond. He therefore ordered Jackson to begin a rapid campaign in the Shenandoah Valley close to the Northern capital. The equivalent of three Federal divisions was sent to the valley to destroy Jackson. Lincoln and Stanton, using the telegraph and what military knowledge they had acquired, devised plans to bottle up Jackson and destroy him. But Federal forces in the valley were not under a locally unified command. They moved too slowly; one force did not obey orders strictly; and directives from Washington often neglected to take time, distance, or logistics into account. Also, in Stonewall Jackson, the Union troops were contending against one of the most outstanding field commanders America has ever produced. Jackson's philosophy of war was: "Always mystify, mislead, and surprise the enemy, if possible; and when you strike and overcome him, never give up the pursuit as long as your men have strength to follow; for an army routed, if hotly pursued, becomes panic-stricken and can then be destroyed by half their number."

The Shenandoah Valley was essential to both sides. It provided the rebels with critical agricultural provisions and was crucial in the Union's defense of Washington, D.C. As a result, the Union Army attempted to hold it with 23,000 troops while General Jackson and his force of 10,000 maneuvered rapidly throughout the region. The valley took on additional importance when General McClellan began his advance on Richmond during the Peninsula Campaign, because McClellan pulled troops out of the valley to reinforce his move against the Confederate capital. Jackson responded quickly, using the mountains as shields to his operations and crisscrossing through various gaps and passes to appear unexpectedly near the surprised Union forces. He began by making a long forced march to strike the Union position at Kernstown on March 23, 1862. The tactical victory that resulted not only threw the Federals off balance, but it also prevented troops from being transferred to the Union invasion and thus kept a full Union corps of 40,000 men under General McDowell from joining the Peninsula Campaign. This movement along with several other forced marches during the campaign earned Jackson's men the epithet "foot cavalry" for their ability to cover great distances to strike the Union at its weakest points.