[1][2] He graduated from the United States Military Academy at West Point, New York in 1853, forty-first in a class of fifty-two.

[2][5][6] In November 1861, Walker was promoted to lieutenant colonel of the 40th Virginia Volunteer Infantry Regiment.

[1][2][4] He was assigned to command of a convalescent camp and then to the Defenses of Richmond, Virginia, between September 1862 and July 1, 1863.

[1][2][5] Walker served as a brigade commander under Heth until he lost his left foot in the Battle of Spotsylvania Court House on May 10, 1864.

[1][4][5] He was reported to have brought the news of the surrender of General Robert E. Lee and the Army of Northern Virginia at Appomattox Court House on April 9, 1865, to Confederate President Jefferson Davis at Danville, Virginia.

[3][4] Davis ordered Walker to take the Confederate troops at Danville to join the force of General Joseph E. Johnston in North Carolina but Walker apparently did not comply with the futile order[2][4] or was unable to comply with it before Johnston surrendered to Union Major General William Tecumseh Sherman on April 18, 1865 (officially April 26, 1865).