Tuhia he tomokanga mo tenei whitianga - I whakahohehia te 21st Marine Regiment i te Hurae 14, 1942, i Camp Elliot, San Diego, California, engari i whakahaerehia i New River, North Carolina. Ko te nuinga o nga mema tuatahi o te puhi i ahu mai i te 6th Marine Regiment. I whakawhiwhia ratou ki te 3rd Marine Division, engari mai i te Hanuere ki te Pipiri 1943 he roopu motuhake ratou. I te wa o te pakanga, i uru te puhi ki te Pakanga o Bougainville, Pakanga o Guam (Fig. 1) me te Pakanga o Iwo Jima. Whai muri i te hekenga mai o Hapani
I te tau 1945, ka nekehia te 21st Marines ki Guam i reira i whakakorehia ai i te 20 o Tihema 1945.