Rough field operations caused difficult working conditions for 9th Air Force maintenance personnel. Here a crew prepares to use an external heater to warm a P-38’s frozen engine so it can be started while an armorer works on the guns in the nose while atop a makeshift stand. (U.S. Air Force photo)

Railroad yard near Limburg, Germany, struck by 9th Air Force light and medium bombers on Dec. 23, 1944, the first day of good weather during the Battle of the Bulge. Unfortunately, since the rail cars were not marked per the Geneva Convention, Allied POWs in transit sometimes lost their lives in rail attacks. (U.S. Air Force photo)

All smiles as Capt. Lowell Smith thanks a U.S. Army antiaircraft crew for their help. Smith had been attacked by a Bf 109 while returning from a mission. With no ammunition left, he flew low over this gun position, and the crew shot the enemy fighter down. (U.S. Air Force photo)

With no sidewalks or pathways on the rough airfield, Maj. George Brooking found it easier to use skis to go from the briefing tent to his P-47. (U.S. Air Force photo)