This is the second volume in a series of nine chronological histories being prepared by theMarine Corps History and Museums Division to cover the entire span of Marine Corpsinvolvement in the Vietnam War. This volume details the Marine activities during 1965, the year the war escalated and major American combat units were committed to theconflict. The narrative traces the landing of the nearly 5,000-man 9th MarineExpeditionary Brigade and its transformation into the Ill Marine Amphibious Force, whichby the end of the year contained over 38,000 Marines.During this period, the Marines established three enclaves in South Vietnam's northernmostcorps area, I Corps, and their mission expanded from defense of the Da Nang Airbaseto a balanced strategy involving base defense, offensive operations, and pacification. Thisvolume continues to treat the activities of Marine advisors to the South Vietnamese armedkrces but in less detail than its predecessor volume, U. S. Marines in Vietnam, 1954-1964, The Advisory and Combat Assistance Era.The co-author, Mr. Jack Shulimson, is the senior civilian historian on the Vietnamproject. He has been with the division since 1964 and has worked on Vietnam studies since1965. Mr. Shulimson has a MA in history from the University of Michigan and is a PhDcandidate in American Studies at the University of Maryland.Major (now Lieutenant Colonel) Charles M. Johnson was with the History andMuseums Division from September 1972 until September 1973. He has a BA in historyfrom the University of Minnesota and was commissioned in the Marine Corps upongraduation in 1959. Lieutenant Colonel Johnson served two tours in Vietnam, first asCommanding Officer, Battery L, 4th Battalion, 11th Marines from May 1966 until May1967 and then from December 1970 until August 1971 as public information officer in thePublic Information Office, U. S. Military Assistance Command, Vietnam in Saigon. He isnow Commanding Officer, Headquarters and Service Battalion, 1st Force Service SupportGroup at Camp Pendleton, California.E. H. SIMMONSBrigadier General, U. S. Marine Corps (Ret.)Director of Marine Corps History and Museu