One of his most successful, and also most controversial raids – fictionalized by Ernest Hemingway in the short story The Snows of Kilimanjaro – was on 25 December 1917. Catching the Germans off guard, he and Lt. Harold Hudson, his wingman, shot up the airfield of Fliegerabteilung (A) 204, setting fire to one hangar and damaging four German aircraft before dropping a placard wishing their opponents a "Happy Christmas."
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https://en.m.wikipedia.org/wiki/William_George_Barker
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https://en.m.wikipedia.org/wiki/William_George_Barker