The Valley Campaigns of 1864 were American Civil War operations and battles that took place in the Shenandoah Valley of Virginia from May to October 1864. Military historians divide this period into three separate campaigns, but it is useful to consider the three together and how they interacted.

Three Valley Campaigns of 1864
The first campaign started with Grant's planned invasion by Sigel. Sigel was in command of the Department of West Virginia, and his orders from Grant were to move "up the Valley" (i.e., southwest to the higher elevations) with 10,000 men to destroy the railroad center at Lynchburg, Virginia.
Sigel was intercepted by 4,000 troops and cadets from the Virginia Military Institute under Confederate Maj. Gen. John C. Breckenridge and defeated. He retreated to Strasburg, Virginia, and was replaced by Maj. Gen. David Hunter, who later burned VMI in retaliation for the actions of the VMI cadets.
Hunter resumed the Union offensive and defeated William E. "Grumble" Jones, who was killed in the battle. Hunter occupied Staunton, Virginia.
Hunter was foiled in his plan to destroy railroads, canals, and hospitals in Lynchburg when initial units under Jubal A. Early arrived. Hunter, short on supplies, retreated back through West Virginia.

Early's Raid and operations against the B&O Railroad (June – August 1864)
Grant finally lost patience with Early, particularly his burning of Chambersburg, and knew that Washington remained vulnerable if Early was still on the loose. He found a new commander aggressive enough to defeat Early: Philip Sheridan, the cavalry commander of the Army of the Potomac, who was given command of all forces in the area, calling them the Army of the Shenandoah. Sheridan initially started slowly, primarily because the impending presidential election of 1864 demanded a cautious approach, avoiding any disaster that might lead to the defeat of Abraham Lincoln.
Also known as Front Royal or Cedarville. Confederate forces under Richard H. Anderson were sent from Petersburg to reinforce Early. Brig. Gen. Wesley Merritt's Union cavalry division surprised the Confederate columns while they were crossing the Shenandoah River, capturing about 300. The Confederates rallied and advanced, gradually pushing back Merritt's men to Cedarville. The battle was inconclusive.
Also known as Flowing Springs or Cameron's Depot. Early and Anderson struck Sheridan near Charles Town, West Virginia. Sheridan conducted a fighting withdrawal.
Two Confederate divisions crossed Opequon Creek and forced a Union cavalry division back to Charles Town.
A minor engagement in which Early attempted to stop Sheridan's march up the Valley. Early withdrew back to Opequon Creek when he realized he was in a poor position for attacking Sheridan's full force.
Also known as the Third Battle of Winchester. While Early had his forces dispersed, raiding the B&O Railroad, Sheridan struck near Winchester, Virginia. Sustaining ruinous casualties, Early retreated from the largest battle in all three of the campaigns, taking up defensive positions at Fisher's Hill.
Sheridan hit Early in an early-morning flanking attack, routing the Confederates with moderate losses. Early retreated to Waynesboro, Virginia.
With Early damaged and pinned down, the Valley lay open to the Union. And because of Sherman's capture of Atlanta, Lincoln's re-election now seemed assured. Sheridan pulled back slowly down the Valley and conducted a scorched earth campaign that would presage Sherman's March to the Sea in November. The goal was to deny the Confederacy the means of feeding its armies in Virginia, and Sheridan's army did so ruthlessly, burning crops, barns, mills, and factories.
As Early began a pursuit of Sheridan, Union cavalry routed two divisions of Confederate cavalry.
In a brilliant surprise attack, Early routed two thirds of the Union army, but his troops were hungry and exhausted and fell out of their ranks to pillage the Union camp; Sheridan managed to rally his troops and defeat Early decisively.
Having completing his missions of neutralizing Early and suppressing the Valley's military-related economy, Sheridan returned to assist Grant at Petersburg. Most of the men of Early's corps rejoined Lee at Petersburg in December, while Early remained to command a skeleton force. His final action was defeat at the Battle of Waynesboro on March 2, 1865, after which Lee removed him from his command because the Confederate government and people had lost confidence in him.