After the start of the war, Wright took part in the evacuation and destruction of the Gosport Navy Yard (later named the
Norfolk Navy Yard) on April 20, 1861, to prevent its exploitation by
Confederate forces. He was captured during this action, but was released four days later as Virginia had not yet joined the Confederacy and therefore wasn't at war with the United States. Wright began constructing fortifications around
Washington, D.C., before being assigned to the 3rd Division of the Department of Northeast Virginia under
Maj. Gen. Samuel P. Heintzelman. Serving as
chief engineer of the 3rd Division during the
First Battle of Bull Run on July 21, 1861, Wright was promoted to major in August. Promoted to
brigadier general of volunteers the following month, Wright was assigned as chief engineer to Maj. Gen.
Thomas W. Sherman's November 1861 expedition against
Port Royal, South Carolina. His successes while commanding Union troops in operations against
Jacksonville,
St. Augustine, and other military targets on the
Florida coast from February to June 1862 led to his appointment as
major general of volunteers and commander of the
Department of the Ohio in August 1862, and commander of the newly created
Army of the Ohio in March 1863. In this command he played a major logistical role in the repulse of Confederate General
Braxton Bragg's invasion of
Kentucky in 1862. His appointment as major general was not confirmed by the
Senate and was revoked in March 1863. As a brigadier general, he was not considered eligible to command a department and Maj. Gen.
Ambrose Burnside was sent to relieve him. Reporting to Burnside, Wright remained briefly as the commander of the District of Western Kentucky before returning to the East. Wright commanded the VI Corps again during Maj. Gen.
Philip H. Sheridan's
Shenandoah Valley campaign from August 6 to October 16, 1864. Wright directed fighting at
Cedar Creek on October 19 before General Sheridan's arrival. In the
Siege of Petersburg, the VI Corps was the first unit to break through the Confederate defenses, on April 2, 1865. Subsequently, operating under the command of Sheridan, it defeated Confederate forces at
Sayler's Creek on April 6, 1865, resulting in the capture of a large number of Confederate soldiers, including Lt. Gen.
Richard S. Ewell and Major General G. W. Custis Lee, son of Robert E. Lee. For Wright's actions at Petersburg he was promoted to a brevet major general in the regular army. ==Postbellum==