Twenty of his squadron's SBD Dauntless dive bombers were destroyed on the tarmac at Marine Corps Air Station Ewa.

[5] On August 20, Mangrum's dozen Douglas SBD Dauntless dive bombers launched from the deck of the USS Long Island (CVE-1) escorted by Grumman F4F Wildcats from Maj John Smith's VMF-223 to become the first Marine planes to land on the new airfield that had just been constructed.

[1][7] During his first 29 days ashore during the battle, Mangrum flew 28 missions including ten strikes, eight searches and seven reconnaissance patrols in support of both ground and naval forces.

[9] Returning to the United States, he served as commanding officer, Cadet Regiment at Naval Air Training Center, Corpus Christi, Texas from 1943 to 1944.

Mangrum was awarded the Legion of Merit as commanding officer of Marine Aircraft Group 45, based on Ulithi, Western Caroline Islands, until October 1945.

Mangrum was awarded a second Legion of Merit with Combat "V" during the Korean War, 1951, for duty as commanding officer, Marine Aircraft Group 12.

[10] Later, he was awarded the Navy Commendation Medal with Combat "V" as First Marine Aircraft Wing liaison officer to Headquarters, 5th Air Force in Seoul, Korea, in 1952.

He retired June 30, 1967 after being awarded the Navy Distinguished Service Medal at Marine Barracks, Washington, D.C.[1] He died on September 28, 1985, in Southern Pines, North Carolina, at the age of 78.