Nellis departed the U.S. for overseas duty with the 495th Replacement Group on May 21, 1944. He was reassigned to the 513th Fighter Squadron two months later, where he participated in 70 aerial combat missions. He was shot down three times. Most of the missions flown by the 513th Fighter Squadron in 1944 were air-to-ground operations in support of Gen. George Patton’s 3rd Army. Due to the unit’s fast advance through France, the squadron was forced to change airfields constantly, but the constant movement did not hamper its operations: The squadron proved quite effective in the air-interdiction and combat air support role. Nellis was an active member in those missions, receiving two promotions and several awards. On Dec. 18, 1944, the Germans launched a major counteroffensive in the Ardennes Forest area known as the Battle of the Bulge. Because of bad weather, the 513th Fighter Squadron was unable to provide air support until Dec. 23. Most of the action occurred within 10 miles of the city of Bastogne, Belgium. Missions conducted in the area were considered extremely hazardous. The fighter squadron flew sorties from dawn to dusk in support of the 101st Airborne Division until Dec. 29. It was in this environment that Nellis flew his final combat mission.
On Dec. 27, 1944, Nellis was hit by ground fire while strafing a German convoy over Luxembourg. His plane burst into flames and plunged to the ground. Nellis was not seen exiting the aircraft, but his sacrifice was not in vain. The missions undertaken by the 513th Fighter Squadron saved many lives and destroyed irreplaceable German armored vehicles, personnel and supplies.
In April 1949, the Air Force began its Memorial Program to honor certain individuals who distinguished themselves serving their country. The Air Force began receiving and evaluating recommendations for memorializing outstanding deceased military personalities who distinguished themselves to such an extent that the nation wished to perpetuate their memory by naming military air installations in their honor. Local civic organizations unanimously chose to honor Nellis, and on April 30, 1950, officially renamed Las Vegas Air Force Base as Nellis Air Force Base. A dedication ceremony to mark the occasion took place May 20, 1950, with Lt. Nellis’ family in attendance.