In December 1943 the 72nd Fighter Squadron in their P-39s were catapulted from the deck of the Escort aircraft carrier USS Nassau (CVE-16) and landed at Makin atoll on the island of Butaritari.

At the completion of the Gilbert and Marshall Islands campaign the 72nd FS was transferred to the newly activated 21st Fighter Group to prepare for the job of escorting the Boeing B-29 Superfortresses over Japan.

On Saipan the 318th had the dubious distinction along with the 21st Fighter Group on Iwo Jima of being the only Army Air Force units to engage in ground combat.

The squadrons of the 318th Fighter Group were attacked by Japanese ground forces in June 1944 on Aslito Airfield, Saipan (renamed Isley Field), sustaining modest casualties.

However, in the 7th Air Force's heaviest losses since 7 December 1941, the 21st Fighter Group was besieged in their tent camp on Iwo Jima before dawn on 26 March 1945.

Pilots and ground personnel took a crash course in infantry tactics and finally destroyed the superior enemy force, but suffered 15 dead and 50 wounded in doing so.

The 318th Group was officially credited with 164 air combat victories by 15 August cease fire, with less than 6 pilots shot down by enemy planes.