In late1944 the US Marine Corps prepared for the toughest battles of the war. It had grown to 35,598 officers, 5,384 officer candidates, and 366,353 enlisted Marines, totaling 431,573 personnel, and now comprised of two amphibious corps, six divisions, 26 non-divisional artillery battalions, and numerous support and service units. Following on from Battle Orders 1 and 7, this book examines the continuing development of the Corps' organization, its training, tactics, weaponry, and command structure. It details the formation of the 5th and 6th Marine Divisions and the 1st Provisional Marine Brigade, and examines the Corps' performance in the brutal battles on Guam, Peleliu, Iwo Jima, and Okinawa, and its deployment as an occupation force.