Gilbert Mouzon O'Brien grew up in Charleston. Prior to the United States entering World War II, he worked as a draftsman for the US Navy Department. In April 1942, he officially enlisted in the Army Air Corps Reserves. On 20 May 1943, he graduated from flight training, received his pilot wings, and was commissioned as a Second Lieutenant

Later in 1943, he was assigned to the 362nd Fighter Squadron, 357th Fighter Group. At the time, the unit was stationed at Hamilton Field, California, where O'Brien initially built up his fighter pilot flight hours training on the P-39 Airacobra.

By late autumn of 1943, O'Brien and the rest of the 357th FG packed up and deployed overseas to Leiston, England. Shortly after their arrival, the group traded their P-39s for the brand-new P-51 Mustangs, setting the stage for his frontline combat tour in early 1944.

The aircraft had the fuselage codes G4-Q. As part of the 357th FG, it featured thered-and-yellow checkered nose band behind a red and yellow spinner, with an Olive Drab upper body and Neutral Gray underside. Note the nose art, which features the name "Shanty Irish" written in unique balloon lettering right next to a green shamrock.

During his By the time he finished his 10-month combat tour in September 1944, he had accumulated 55 mission marks and 8 victory swastikas painted on the side of his Mustang accounting for his 7 confirmed solo kills plus shared credits.

Here follows his complete 1944 Victory Claims List:

March 6, 1944: O'Brien scored a confirmed single victory against a Messerschmitt Bf 109 during a major Eighth Air Force escort mission over Berlin and central Germany.

May 8, 1944: One Focke-Wulf Fw 190

May 27, 1944: O'Brien shot down a Bf 109 during a fierce dogfight. His official combat encounter report captures the intensity of the moment: "I slid right up beside him with my flaps down. He bailed out as I was alongside of him, at about 12,000 ft. His chest was covered with blood and he hit the rudder."

June 29, 1944: O'Brien officially achieved Ace statuson this day when he downed a Bf 109 and he teamed up with another pilot to share downing of the twin-engine Me 410.

August 5, 1944: One Focke-Wulf Fw 190, this would be his final confirmed aerial victory of the war.

This profile is one of many newly made P-51 Mustangs made during the last three months, more will follow soon.