Of the three regiments the Twenty Second Marines was the oldest. It was formed at San Diego in June, 1942, and the following month left for Samoa where it remained as a part of the defense force until the fall of 1943. After an extensive training period the regiment left Samoa and sailed to the island of Hawaii to prepare for the Marshalls Campaign. During the Kwajalein phase it acted as a reserve and after the rapid capture of Roi and Namur by the Fourth Marine Division, the Twenty Second Marines, in accordance with the resulting speed-up in the Central Pacific timetable, went on to assault Eniwetok in the Western Marshalls. After a brief but bloody fight for Eniwetok, the regiment seized and occupied numerous adjoining islands. From Eniwetok the Twenty Second Marines went to Guadalcanal and trained there for the Guam Campaign. On 21 July 1944, the regiment landed on Guam on W-Day as a part of the First Provisional Brigade. It drove inland against heavy resistance and then turned to seal off Orote Peninsula. In conjunction with the Fourth Marines, the Twenty Second drove the length of the peninsula and destroyed the enemy emplaced there.
Activated on 8 January 1944, the Fourth Marines was formed from veteran units—the four Marine Raider Battalions. It took its name from the famous Marine regiment that had been lost on Bataan. Its officers and men had seen action at Tulagi, Guadalcanal, Makin, New Georgia, Bougainville; later at Guam, and abreast of the Twenty Second Marines the new regiment received as such, its baptism of fire, when it landed on 21 July 1944. After fighting its way inland and seizing Mt. Alifan, the regiment joined the Twenty Second to reduce heavily defended Orote Peninsula. The Fourth Marines had been on one operation previous to Guam; it had seized the island of Emirau in the St. Matthias Group, and although the operation was bloodless, it was a triumph in planning and execution.
On 1 May 1944, the major part of the Twenty Ninth Marines was activated at Camp Lejeune, New River, North Carolina. Two battalions were formed from the pick of officers and men in the eastern part of the United States at that time. These battalions were composed of some veterans but the greater part had no previous combat experience. With reinforcing elements, the regiment (less its First Battalion) crossed the United States by rail and sailed to Guadalcanal in August. The First Battalion joined the regiment on Guadalcanal in early October. It had been activated from Second Marine Division troops on Hawaii in February, 1944. First called the Second Separate Infantry Battalion, it trained for a brief time on Hawaii and then went to Saipan for that operation, attached to the Second Division. Landing on D-Day the battalion, now called the First Battalion, Twenty Ninth Marines, was attached to the Eighth Marines and to it fell the task of capturing Mt. Tapotchau, the commanding terrain on Saipan. Its losses were heavy—over 60%—and the battalion therefore was not used in the Tinian operation, which followed.
From the reinforcing elements of the First Provisional Brigade were formed, in large part, the Sixth Tank Battalion, Sixth Pioneer Battalion, the Sixth Engineer Battalion, and the division’s artillery regiment, the Fifteenth Marines.
2. TRAINING AND PREPARATIONS
When the Sixth Marine Division began its training program for its first—and only—operation, it had several initial advantages: Over two thirds of its officers and men were veterans, well schooled in the ways of the wily Japanese; it started off with the experience gained from nearly four years of war; the structure of the entire division was organized to benefit from this experience. Through October, 1944, and on into February, 1945, the division trained vigorously. Special emphasis was placed on individual marksmanship, combat firing exercises employing all weapons and arms, night problems, flame-thrower-demolition teams, tank-infantry problems, and air-ground problems. Training was concluded with an eight day division problem illustrating tactical principles for large unit employment. All through the training period General Shepherd strove to indoctrinate his division with the spirit of attack; that it was cheaper to drive ahead in unrelenting assault than to hesitate trying to find easier ways of achieving the objective while troops remained in contact with the enemy. This indoctrination was to pay dividends on Okinawa when forward progress seemed impossible.
3. MOVEMENT TO TARGET
During the period 1-6 March 1945, the Sixth Marine Division was aboard ship engaged in amphibious landing rehearsals for the Okinawa operation. On the first day troops practiced debarkation and deployment of landing craft; on the next two days the two assault regiments, the Fourth and Twenty Second, landed on the beaches of Guadalcanal and practiced limited maneuvers ashore. Then followed a critique and on the next day there was a full-scale dress rehearsal. Although limited in their extent, the rehearsals were quite satisfactory.
After breaking camp ashore, the division re-embarked to sail for the staging area, Ulithi, on 15 March. At Ulithi, a little atoll in the Caroline Islands, the division joined the enormous task force assembling there for the invasion of Okinawa. Training was carried out aboard ship and final preparations made for the target. By now the troops were aware of their destination and the force designated to land there. They were told that the Sixth Marine Division would land simultaneously with, and on the left of, the First Marine Division, as a part of the III Amphibious Corps. South of the Marines a corps of Army, the XXIV, would land. Both of the corps were components of a larger force—the new Tenth Army.
On the way to Ulithi, while there, and on the way to the target the men were given a thorough briefing. General Shepherd made it plain that every man should know not only his assigned task, but that of his own unit, and of adjacent units, as well as the general scheme of maneuver. In the briefing aboard ship the men learned that Okinawa had a population of some 450,000 civilians; that there were roughly 70,000 Japanese soldiers on the island. They also learned something about its geography, its towns, roads, rivers and terrain.