This is the fourth volume in a planned 10-volume operational and chronological series covering the U.S. Marine Corps' participation in the Vietnam War. A separate topical series will complement the operational histories. This volume details the change in focus of the III Marine Amphibious Force (III MAF), which fought in South Vietnam's northernmost corps area, I Corps. III MAF, faced with a continued threat in 1967 of North Vietnamese large unit entry across the Demilitarized Zone separating the two Vietnams, turned over the Chu Lai enclave to the U .S. Army's Task Force Oregon and shifted the bulk of its forces-and its attention-northward. Throughout the year, the 3d Marine Division fought a conventional, large-unit war against the North Vietnamese Army (NVA) near the demilitarized zone. The 1st Marine Division, concentrated in Thua Thien and Quang Nam provinces, continued both offensive and pacification operations. Its enemy ranged from small groups of Viet Cong guerrillas in hamlets and villages up to formations as large as the 2d NVA Division. The 1st Marine Aircraft Wing provided air support to both divisions, as well as Army and allied units in I Corps. The Force Logistic Command, amalgamated from all Marine logistics organizations in Vietnam, served all, major Marine commands. This volume, like its predecessors, concentrates on the ground war in I Corps and II I MAF's perspective of the Vietnam War as an entity. It also covers the Marine Corps participation in the advisory effort, the operations of the two Special Landing Forces of the U.S. Navy's Seventh Fleet, and the services of Marines with the staff of the U.S. Military Assistance Command, Vietnam. There are additional chapters on supporting arms and logistics, and a discussion of the Marine role in Vietnam in relation to the overall American effort. The nature of the war facing III MAF during 1967 forced the authors to concentrate on major operations, particularly those characterized by heavy combat. The uneven quality of the official reports submitted by combat units also played a role in selecting the materials presented in this volume. This is not meant to slight those whose combat service involved long, hot days on patrol, wearying hours of perimeter defense, an d innumerable operations, named and un-named . These Marines also endured fights just as deadly as the ones against large enemy regular units. III MAF's combat successes in 1967 came from the efforts of all Americans in I Corps.