Explanation: Gen. Grant wanted to disrupt Confederate communications in the Shenandoah Valley. He was still having trouble with Gen. Lee's Army of Northern Virginia.
In March 1864, Lt. Gen. Ulysses S. Grant assumed overall command of the Union armies, east and west. In May, he ordered Maj. Gen. Franz Sigel to cooperate with the Army of the Potomac's spring offensive by advancing up the Valley to disrupt Confederate communications at Staunton and Charlottesville. On May 15, while Grant and Lee were locked in desperate combat at Spotsylvania Courthouse, Sigel made contact with a Confederate force under former vice president of the United States John C. Breckinridge at New Market. Sigel was defeated and retreated rapidly beyond Strasburg, crossing Cedar Creek by dusk on May 16. Grant then replaced Sigel with Maj. Gen. David ``Black Dave'' Hunter, who was given the task of cutting the Virginia Central Railroad.
In the meantime, Breckinridge's division had been called east to reinforce the Army of Northern Virginia at Hanover Junction, and Brig. Gen. William E. ``Grumble'' Jones assumed command of the remaining Confederate forces in the Valley. On June 5, Hunter crushed the smaller Confederate army at Piedmont, killing Jones and taking nearly 1,000 prisoners. The disorganized Confederates could do nothing to delay Hunter's advance to Staunton, where he was joined by reinforcements marching from West Virginia.
From Staunton, Hunter continued south, sporadically destroying mills, barns, and public buildings, and condoning widespread looting by his troops. On June 11, Hunter swept aside a small cavalry force and occupied Lexington, where he burned the Virginia Military Institute and the home of former Virginia Governor John Letcher. Hunter's successes forced Lee to return Breckinridge and to send the Second Corps of the Army of Northern Virginia under Lt. Gen. Jubal A. Early to the defense of Lynchburg. Sending Early to the Valley was a desperate decision that restricted Lee's ability to undertake offensive operations against Grant on the Richmond-Petersburg front.
On the afternoon of June 17, Hunter's army reached the outskirts of Lynchburg, even as Early's vanguard began to arrive by rail from Charlottesville. After a brief, but fierce engagement, Hunter retreated into West Virginia. Early pursued for two days, but then returned to the Valley and started his troops north to the Potomac River.