In the capture of the southern Marianas, including the recapture of Guam, during the summer of 1944, Army ground and air forces played an important, though subordinate, role to that of the Navy and its Marine Corps. Marine personnel constituted the bulk of the combat troops employed. The objective of this campaign was -to secure control of sea communications through the Central Pacific by isolating and neutralizing the Carolines and by the establish-ment of sea and air bases for operations against Japanese sea routes and long-range air attacks against the Japanese home land.- Its success would pro-vide steppingstones from which the Americans could threaten further attack westward toward the Philippines, Formosa, and Japan itself, and would gain bases from which the Army Air Forces' new very long range bombers, the B-29's, could strike at Japan's heartland. Recognizing and accepting the chal-lenge, the Japanese Navy suffered heavy and irreplaceable losses in the accompanying Battle of the Philippine Sea; and the islands after capture became the base for all the massive air attacks on Japan, beginning in November 1944. In the operations described in the present volume, landings against strong opposition demonstrated the soundness of the amphibious doctrine and tech-niques evolved out of hard experience in preceding Pacific operations. Bitter inland fighting followed the landings, with Army and Marine Corps divisions engaged side by side. The author's account and corresponding Marine Corps histories of these operations provide ample opportunity to study the differences in the fighting techniques of the two services. Dr. Crowl also deals frankly with one of the best-known controversies of World War II, that of Smith versus Smith, but concludes that it was the exception to generally excellent interservice co-operation. With team effort among the military services the order of the day, this record of the Army's experience in working with the Navy and the Marine Corps should be particularly valuable both now and in the future.