This is the first of a series of functional volumes on the Marine Corps' participation in the Vietnam War, which will complement the 10-volume operational and chronological series also underway. This particular history examines the role of the Navy chaplain serving with Marines, a vital partnership of fighting man and man of God which has been an integral part of the history of the Marine Corps since its inception. The first Marine aviation units to support the South Vietnamese Government forces entered Vietnam in 1962 and with them came their chaplains. When major Marine ground forces were first assigned to Vietnam in 1965, the number of assigned chaplains increased apace. By 1968 the III Marine Amphibious Force, occupying the five northernmost provinces of South Vietnam, numbered over 80,000 Marines and had under its command the better part of three Marine divisions, a greatly expanded Marine aircraft wing, and a U.S. Army corps of multi-divisional strength. The number of Navy chaplains serving ashore with Marine units exceeded all past experience, and the scope of their ministry had expanded into new and sometimes troubling fields. When the American involvement in the war gave way to Vietnamization, Marine units phased down in strength, eventually departing the country from 1969-1971. Then, as today, they stood ready in the Pacific, on board ship and at bases in Okinawa, Japan, Hawaii, and California, to provide, as needed, a ready force to meet their country's call. And with them, as always, stood their chaplains, in peace or war ready to provide the counsel, comfort, and religious experience that are so much a part of military life.