This volume, the latest published by the Office of Air Force History in the United States Air Force in Southeast Asia series, looks at the Air Force's support of the ground war in South Vietnam between 1965 and early 1968. The book covers the period from the time when the United States began moving from an advisory role into one of active involvement to just before the time when the United States gradually began disengaging from the war. The final scene is the successful air campaign conducted during the Communists' siege of the Marine camp at Khe Sanh. While the actual siege lasted from late January to the middle of March 1968, enemy preparations for the encirclement-greatly increased truck traffic and enemy troop movements- were seen as early as October 1967. A subsequent volume in the Southeast Asia series will take up the story with the Communists' concurrent Tet offensive during January and February 1968.