On August 16, 1917, Warman shot down a two-seater and a balloon before engaging three German scouts. When his machine gun jammed and couldn't be cleared, he threw his gun mallet at his opponents and resumed the fight with his flare pistol. For his actions, Warman was awarded the Distinguished Service Order (DSO). He was the only American to receive this award during World War I. While serving with the Royal Canadian Air Force, Warman died from injuries sustained in a crash at Chingford on May 8, 1919.

Distinguished Service Order (DSO)
"For conspicuous gallantry and devotion to duty. During two days whilst operating under difficult conditions in high wind and against strong enemy opposition, he destroyed three enemy machines and a balloon. He displayed the greatest dash and fearlessness in attacking an enemy aerodrome and on one occasion, when separated from his patrol and surrounded by twenty machines, he fought his way through, although his machine gun was useless, by attacking with his Verey pistol; eventually regaining his own aerodrome with his machine much shot about. His wonderful coolness and courage have on all occasions been beyond praise." DSO citation, London Gazette, January 9, 1918

Military Cross (MC)
"For conspicuous gallantry and devotion to duty. He has on all occasions proved himself to be an exceptionally skilful and gallant pilot, having in the space of six weeks brought down six machines and destroyed a hostile balloon. He has also driven down at least five other enemy machines, displaying a consistent determination to attack at close range regardless of personal danger." MC citation, London Gazette, September 26, 1917