The division echeloned into Auckland, New Zealand between January and March 1943. In June of that year they moved onto Guadalcanal for additional training. 27 September 1943 saw the division land as part of the Battle of Bougainville and fight on the island until their last unit to arrive, the 21st Marine Regiment, embarked on 9 January 1944. During the course of the battle the division had approximately 400 Marines killed.
They returned to Guadalcanal in January 1944 to rest, refit and train. The next operation the division took part in was theBattle of Guam. From 21 July 1944 until the last day of organized fighting on 10 August, the division fought through the jungles on the island of Guam. During these 21 days of fighting, the Division captured over 60 square miles (160 km2) of territory and killed over 5,000 enemy soldiers. The next two months saw continuous mopping up operations in which the Marines continued to engage left over Japanese forces. At the end of the battle the Division had sustained 677 Marines killed, 3,626 wounded and 9 missing.
The Division remained on the island of Guam for training purposes until they embarked as part of the landing force for the Battle of Iwo Jima. The 3rd Marine Division was initially in reserve for the battlehowever they were committed one regiment at a time as the initial regiments that landed needed to be relieved. The 21st Marines came ashore on 20 February followed by the 9th Marines and a reinforcement BN. of the 3rd Marines on 25 February. The Marines of these two infantry regiments, supported by the artillery of the 12th Marine Regiment and tanks of the 3rd Tank Battalion, fought on Iwo Jima until the end of organized resistance on 16 March and the subsequent mopping up operations for the next month. All elements of the Division were back on Guam by 17 April 1945. The fighting on Iwo Jima would cost the 3rd Marine Division 1,131 killed in action and another 4,438 wounded.
After the return to Guam, the Division began preparing for the invasion of Japan. This however never took place as Japan surrendered in August 1945. The Division was deactivated on 28 December 1945
The Division was reactivated on 7 January 1952 at Camp Pendleton, California. Immediately after its activation and still in its organizational state, the Division began intensive combat training, including new tactics and maneuvers based on lessons learned in Korean War. During the remaining part of 1952 elements of the Division participated in numerous exercises and training problems, including vertical envelopment (helicopter landing), airborne operations and attack, and defense against atomic weapons and missiles.
In August 1953 the Division arrived in Japan to support the 1st Marine Division in the defense of the Far Eastern area. In March 1956 the Division moved to Okinawa and remained there in a readiness posture until 1965