After graduation from West Point (1853), he saw varied service on the frontier. In the Civil War, Sheridan, made colonel of the 2d Michigan Cavalry (May, 1862), took part in the Union advance on Corinth, Miss., under General Halleck and won a victory over Confederate cavalry at Booneville, Miss., on July 1, 1862. Made a brigadier general of volunteers and given command of a division of the Army of the Ohio, Sheridan distinguished himself under Don Carlos Buell at Perryville (Oct., 1862) and was promoted to major general of volunteers (Dec., 1862) for his able conduct under William S. Rosecrans at Murfreesboro.
In the Chattanooga campaign (1863) he aided George H. Thomas in holding off the Confederates at Chickamauga and had a prominent part in the Union victory at Missionary Ridge. Ulysses S. Grant recognized his ability and appointed Sheridan commander of the cavalry corps of the Army of the Potomac (Apr., 1864). In a notable raid (May 9–24, 1864) in the Wilderness campaign, he destroyed communications and supplies behind Robert E. Lee's lines and defeated J. E. B. Stuart at Yellow Tavern.
The success of the Confederate general Jubal A. Early in the Shenandoah Valley prompted Grant to give Sheridan command of the Union forces there in Aug., 1864. At Winchester (Sept. 19) and Fishers Hill (Sept. 22) Sheridan roundly defeated Early and drove him up the valley. Sheridan then slowly withdrew, systematically laying waste to the Shenandoah so that, as he reported, even a crow flying over the place would have to take his rations with him. But Early advanced again, and on the morning of Oct. 19, while Sheridan was at Winchester, 15 mi (24 km) away, he surprised the Union forces at Cedar Creek and drove them back. Upon hearing of the defeat Sheridan hurried to the field, rallied his men, and, counterattacking, won a decisive victory. (This success was highly dramatized by Thomas Buchanan Read in his poem, "Sheridan's Ride.") Sheridan was made a major general in the regular army in Nov., 1864.
In Mar., 1865, Gen. George Custer of Sheridan's army defeated the remains of Early's command at Waynesboro. Sheridan then moved eastward, destroying Confederate communications as he went. After his victory at Five Forks (Apr. 1, 1865), he pursued Lee vigorously and cut off the Confederate retreat at Appomattox, forcing Lee's surrender.