Marshall began his military career as an aviation cadet in 1942. He completed flight training at
Yuma Army Air Base in Arizona, and received his
pilot's wings and commission as a
second lieutenant in April 1943. Assigned to
Las Vegas Army Air Field in Nevada, he began as a pilot with the
326th Fighter Gunnery Training Group before becoming chief of the
Bell P-39 Airacobra Training Section there. In February 1945 he went to the
Panama Canal Zone as a pilot with the
28th Fighter Squadron and as operations officer of the
32nd Fighter Squadron, later redesignated the
23rd Fighter Squadron,
36th Fighter Group. Marshall shot down two more MiG-15s, including a shared destruction, on November 28. One of these fighters was flown by German Shatalov, a
Soviet flying ace with five aerial victories against U.S. aircraft. On November 30, 1951, the 335th Fighter-Interceptor Squadron and other squadrons within the
4th Fighter-Interceptor Wing intercepted a
People's Liberation Army Air Force aerial formation consisting of nine
Tupolev Tu-2 bombers and 16
Lavochkin La-11s, that was attempting an aerial raid on the
Cho'do Island. Marshall shot down one Tu-2 and one La-11, crediting with his fourth and fifth aerial victories and thus earning the title of
flying ace. As he was attempting to shoot another La-11, which was flown by Chinese pilot Wang Tianbao, Marshall overshot as the La-11 turned hard left, resulting in the La-11 making a long deflection shot which struck the left wing of Marshall's F-86. Wang saw the F-86 going down in a spin and claimed an F-86 kill, after he returned back to his base in
Northeast China. However, Marshall managed to regain consciousness and recovered his F-86 from the spin. He flew his crippled aircraft to
Suwon Air Base, where it was repaired and Marshall was treated for his wounds. For his heroism during the aerial combat on November 30, he was awarded the
Silver Star. After his recovery, Marshall continued flying combat missions. He shot down his fourth MiG-15 and sixth overall aerial victory on December 5, 1951. Marshall became the fifth jet ace of the
Korean War, credited with 6 1/2 enemy aircraft destroyed, seven probable, and six damaged, while flying 100 missions. In January 1952, he returned to the United States to command the
93rd Fighter-Interceptor Squadron at
Kirtland Air Force Base in New Mexico. In July 1954, Marshall became chief of the Central Air Defense Force Tactical Evaluation Board at
Richards-Gebaur Air Force Base in Missouri, where he established the first tactical evaluation system in the
Air Defense Command; developed the first wind-driven tow reel target system; and headed a team of military and civilian technicians that extended radar search capability (later known as the Marshall fix) of fighter-interceptor aircraft from . In 1957, he was chief of the Central Air Defense Force
Bendix Trophy Race Team flying the
F-102 Delta Dagger, with his team taking first and second place. Marshall was promoted to the grade of
lieutenant general effective September 1, 1974, with date of rank August 27, 1974. He was appointed vice commander in chief of the Pacific Air Forces, in September 1974. His final assignment was as Deputy Commander in Chief of U.S. Readiness Command at
MacDill Air Force Base in Florida, from June 1975 until his retirement on September 1, 1977. ==Later life==