He was born in Durant, Bryan County, Oklahoma. He entered the service from Boulder county, Colorado. He was half Native American of the Choctaw Tribe. His great grandparents had walked the infamous Choctaw Trail of Tears.

He enlisted in 1939 in the Oklahoma National Guard. When he served In the airborne invasion of Sicily, Turnbull’s plane crashed and later he sustained a life threatening abdominal gunshot wound. This alone could have been his ticket home, but he chose to rejoin his men for the D-Day invasion.

At some point First Lt. Turnbull and ten of his men were crawling along a hedgerow, with Turnbull in the lead. They heard one of the many artillery shells coming but in their exposed position, there was no place to go but "flatten out." In a thunderous explosion First Lt. Turnbull was killed by the deadly shrapnel.

1LT Turnbull is buried or memorialized at Plot E Row 21 Grave 21, Normandy American Cemetery, Colleville-sur-Mer, France

The following more detailed history is from a LinkedIn profile, June 7, 2022, Joel Everidge

Turner Turnbull III was the youngest of three children, born in Durant, Oklahoma in 1921. His mother, Lucille McCarty Turnbull, died when he was only five, and he was orphaned at about 15 when his father Walter J. Turnbull, Sr. died. Up to this point, he, his brother Walter Turnbull, Jr. and sister Beulah Margaret Turnbull had lived in Durant with their grandmother Adeline Dwight Turnbull, at the Turnbull ranch at Caddo and with their aunt Margaret McBee in Durant.

As half Choctaw, Turner was a member of one of the proudest of Choctaw families; his great grandparents, Turner B. Turnbull, Sr. and Angelico "Jerico" Perkins, walked the infamous Choctaw Trail of Tears. In 1914, young Turner's father, Walter J. Turnbull, Sr., at age 28, was the youngest Choctaw Chief ever elected by popular vote, but was not allowed to serve. Federal rule stated that chiefs had to be at least 35 years of age. A well-educated and brilliant lawyer, Walter served two terms as District Attorney of Bryan County.

With the death of his father, Turner went to live with another aunt in Colorado, where he finished high school. It is also thought he and his brother attended Haskell Indian School in Kansas. He came back to Oklahoma to attend Bacone Indian School at Muskogee and while there enlisted in 1939 in the Oklahoma National Guard.

A year later, while still a student, he was inducted into the active military service with the 45th Division. He was commissioned a 2nd Lieutenant after graduating from Officers' Training (Candidate) School at Fort Benning, Georgia. Chronicles of Oklahoma.

First Lt. Turnbull was a paratrooper in the famous elite all-volunteer 82nd Airborne Division and served in the African, Sicilian, and Italian campaigns. The soldiers of the 82nd were a little older than the average GI and most were of better than average education. In the airborne invasion of Sicily, Turnbull's plane crashed, probably shot down by friendly fire. In Sicily he sustained a life threatening abdominal gunshot wound and was hospitalized in England for four months. Awarded the Order of the Purple Heart for his wound, this alone could have been his ticket home, but he chose to rejoin his men for the D-Day invasion.

Under the cover of darkness, his 2nd Battalion/505th Regiment 82nd Airborne Division parachuted into France behind German lines very near Ste. Mere Eglise [just inland from Utah beach] about 1:45 a.m. on the morning of June 6, 1944, approximately four hours before the massive U.S. offensive on the beaches of Normandy. His regiment helped liberate the town and shut down the German communications center.

Because a major German assault was expected from the north, the 2nd Battalion was ordered to proceed to the hamlet of Neuville-au-plain, capture it, and set up a defensive line to protect the stronghold of Ste. Mere Eglise. Short on manpower, the battalion commanding officer Lt. Col. Benjamin Vandervoort, trusting in Turnbull's reputation for military leadership, gave the Neuville-au-plain assignment to Turnbull and his small platoon of men.

First Lt. Turnbull was ordered to take his platoon of about 35 (other sources say 42) men to set up a perimeter about 2 miles from the drop. This was the main road to Utah Beach and the ones who owned the road would clearly be in a very superior strategic position at the most critical time of the invasion. Unbelievably, this small group successfully defended the road. They held the full regiment of the German l058th Grenadiers at bay for approximately eight long hours (the whole day well into the late afternoon).

At some point First Lt. Turnbull and ten of his men were crawling along a hedgerow, with Turnbull in the lead. They heard one of the many artillery shells coming but in their exposed position, there was no place to go but "flatten out." In a thunderous explosion First Lt. Turnbull was killed by the deadly shrapnel. John Keegan, in his book, Six Armies In Normandy, observed that, "Turnbull belongs not only with the brave, but [is] among those who saved the invasion."

S.L.A. Marshall, the European Theater of Operations historian states in his report that "By its all-day stand, the platoon had kept the Ste. Mere Eglise force from being hit simultaneously from north and south during the most critical hours of D-Day, and by providing this breathing space to the major defensive base of the Division, [the platoon] had helped immeasurably to stabilize the position of an entire (VII) Corps."

Stephen Ambrose, in his book "D-Day June 6, 1944", pointed out that Turnbull's "heroic stand allowed the 3rd Battalion, 505 PIR and 2nd Battalion, 505 PIR, to concentrate on resisting an even stronger counterattack from the German 795th Regiment south of Ste. Mere Eglise. It was as big a counterattack as the Germans mounted on D-Day."