Confederate General Richard S. Ewell defeats a Union garrison at the Shenandoah Valley town of Winchester, Virginia, from June 13 to 15.

After the Battle of Brandy Station on June 9, Lee had ordered Ewell's nineteen thousand-man Second Corps, Army of Northern Virginia, to clear the lower Shenandoah Valley of Union opposition so that Lee's army can proceed on its invasion of Pennsylvania, shielded by the Blue Ridge Mountains from Union interference.

Union General-in-chief Henry Wager Halleck has expressed great concerns about the Middle Department's defensive strategy for its primary objective of protecting the Baltimore and Ohio Railroad corridor.

Brigadier General Benjamin Franklin Kelley, commander of the "railroad division" (Department of Harper's Ferry), had been advised that his plan, along with Major General Milroy's and Major General Robert C. Schenck's (Commander of the Middle Department), was unsound.

The victory at Second Winchester clears the Valley of Federal troops and opens the door for Lee's second invasion of the North.

The capturing of ample supplies justifies Lee's conceptual plan to provision his army on the march.

The Federal defeat stuns the North, and Secretary of War Edwin M. Stanton will call for additional militia to be federalized.

Shortly afterward, President Lincoln requests one hundred thousand volunteers to repel the threatened invasion.

Several fleeing members of the scattered 87th Pennsylvania hastily tramp back to their homes near Gettysburg and in adjoining York County, Pennsylvania, spreading news to local officials that the Confederates are now in the Valley in strength, with apparent designs on invading Pennsylvania.

Governor Andrew Curtin of Pennsylvania, in response to these reports and other military intelligence, calls for fifty thousand volunteers to protect the Keystone State.