Commissioned as a Colonel in the Sixth Virginia Cavalry, of the Confederate Army, in 1861, Field was promoted to brigadier general within the first year of the war. In 1862, he fought at Mechanicsville, and at Cedar Mountain. He was wounded at First Manassas, and never fully recovered. In 1864, he was promoted to major general in command Hood's Texas division. He participated in the battles at Cold Harbor and Petersburg. His division, half of Lee's army, and stood as only effective fighting unit intact upon surrender at Appomattox Courthouse.