Joining the 2nd Armored Division in January 1942, White first commanded the division's reconnaissance squadron as a major, then served at successively higher levels in combat. He led the 67th Armored Regiment in fighting in North Africa, then commanded Combat Command B in Sicily and, as a brigadier general, in the fighting across Europe. That unit surrounded and destroyed much of the 2nd Panzer Division during the Battle of the Bulge, cutting off the German penetration at its farthest advance. By early 1945, White had risen to major general and command of the division.
After the war, White commanded the Cavalry School at Fort Riley (1945–1946), the U.S. Constabulary in the Army of Occupation in Germany (1948), and then the Armored Center and School at Fort Knox (1949–1950). An ardent horseman and polo player, he also managed the army equestrian team that competed in the 1948 Olympic Games.
During the latter stages of the Korean War in 1952, White took command of X Corps, then returned to command Fourth Army as a lieutenant general at Fort Sam Houston, Texas. His last assignment was the command of Army Forces, Far East, and Eighth Army (1955–1957), during which he was promoted to full general. Then, following reorganization in the region, he became commander of U.S. Army, Pacific. Retiring in 1961 after over 38 years on active duty, nearly all in command positions, White served as a trustee of Norwich University, as president of the U.S. Armor Association, and as a defense consultant. He died in Hanover, New Hampshire, on 11 June 1990. At his alma mater, the main entry route has been named General I. D. White Avenue in his honor.
Harmon, E. N. Combat Commander: Autobiography of a Soldier. Englewood Cliffs, NJ: Prentice-Hall, 1970.; Patton, Maj. Gen. George S. "Remembering General I. D. White." Armor (September-October 1990): 42–44.; Yale, Wesley W. Alternative to Armageddon: The Peace Potential of Lightning War. New Brunswick, NJ: Rutgers University Press, 1970.