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.