This is the sixth volume in a planned nine-volume operational and chronological series covering the Marine Corps ' participation in the Vietnam War. A separate functional series will complement the operational histories. This volume details the change in United States policy for the Vietnam War. After a thorough review, President Richard M. Nixon adopted a policy of seeking to end United States military involvement in Vietnam either through negotiations or, failing that, turning the combat role over to the South Vietnamese. It was this decision that began the Vietnamization of the war in the summer of 1969 and which would soon greatly reduce and then end the Marine Corps' combat role in the war. The Marines of III Marine Amphibious Force continued the full range of military and pacification activities within I Corps Tactical Zone during this period of transition. Until withdrawn, the 3d Marine Division, employing highly mobile tactics, successfully blunted North Vietnamese Army efforts to reintroduce troops and supplies into Quang Tri Province. The 1st Marine Division, concentrated in Quang Nam Province, continued both mobile offensive and pacification operations to protect the city of Da Nang and surrounding population centers. The 1st Marine Aircraft Wing provided air support to both divisions, as well as other allied units in I Corps, while Force Logistic Command served all major Marine commands.