Sebille joined the US military on the 21st December 1941 after Pearl Harbor in the patriotic rush. He joined the USAAF and began flight training in January 1942. He was commissioned in July of the same year and was assigned to the 450th Bomb Squadron.

The 450th Bomb Squadron was assigned to Britain in 1943 where Sebille flew B-26 Marauder Bombers from 1943-1945. He was promoted to First Lieutenant when the Squadron was assigned to Britain. He is also listed as one of the pilots who flew the first low level attack attempted by B-26s over Europe. In 1943 he was promoted to Captain and he flew many more sorties as Squadron, Group and Wing leader. During the war he was awarded two Distinguished Flying Crosses and twelve Air Medals.

After the war he resigned his commission and became a commercial jet pilot. He flew jets for about a year until he was given an offer to rejoin the USAAF as a Lieutenant.

He was shot while flying a Mustang against an armored convoy attacking UN troops in Korea in August 1950. Though not fatally wounded his aircraft was damaged. He purposefully crashed his plane into the convoy stopping them from advancing, however this cost him his life. For this action he was awarded the Medal of Honor making him the first person in the new American Air Force to receive it.

During World War Two he flew 68 combat missions and is credited with 3000 flying hours, 245 of which were combat hours. He is also credited as being one of the few pilots who survived the war who took part in the first of the B-26 missions from Britain.