A month after the squadron arrived at King's Cliffe, Graham was promoted to Flight Commander a position he maintained until he became the Squadron Operations Officer on the 18th of November, 1943. He flew his first mission on November 5, 1943, while the 79th were attached to the 55th Fighter Group to gain experience. The squadron's inauspicious entry into combat, a major communications problem led to every pilot returning to base early.

Graham drew his first blood in combat on the 31st of December, 1943. Leading the 79th Fighter Squadron as they provided top cover on a mission over the Bordeaux, France area. He dove after two Fw-190s that were spotted well below them. Though he couldn't manage to release his drop tanks, he was able to dive and maneuver behind one of the enemy aircraft. Closing to 350 yards he opened fired and scored numerous hits but was only credited with having damaged the aircraft.

On January 4, 1944 the Massachusetts native was promoted to the rank of Captain. 25 days later he scored his first victories, downing three Fw-190's during an escort mission to Frankfort, Germany. He became the first ace of the 79th Fighter Squadron on February 20th, when he downed two Me-110's in the Koblenz area.

He scored his final ½ victory on March 18th, just moments before he was killed in action. Arthur Heiden, his wingman on that day's mission, wrote: "It was a weird day. I was Graham's wingman and we had bounced a Me-110 right on the deck. We both had made firing passes, but he was a sharp German, flying slow and skidding so he was going other than he appeared to be in and around a bunch of timber. Graham got right on top of him and forced him into the snow covered ground. Two men got out and took off across an open area. Strange, as they were close to timber. Graham made a pass right over them. Then the weird part, he pulled up in a steep chandelle, but the nose fell through and he went straight in and exploded." Graham's aircraft had crashed to earth at Krohwinkel, near Memmingen, approx. 45 miles southwest of Augsburg, Germany.

The 20th Fighter Group felt his loss deeply, as he was one of the hottest pilots they had in their ranks. Known for his natural piloting skills and aggressiveness in combat, many who saw him in action believe he would've been one of the the highest scoring P-38 aces of the ETO if his life had not ended so abruptly. As testament to his skills it has been widely reported that he scored three of his victories using only 583 .50 caliber machine gun rounds and 36 rounds from his 20mm cannon.

His body was buried at St. Avold Cemetery, Metz, France, and was later moved, at the request of his next of kin, to Plot F, Row 7, Grave 28, Lorraine American Cemetery, St. Avold, France.