Why is there little mention of the US Army in Cam Ranh Bay during the Vietnam war?

Cam Ranh Bay was a beautiful seaport, as well as a large military base. The Russian Battleship Fleet anchored there in 1905 enroute to the battle of Tsushima, fought on 27 May 1905. Cam Ranh Bay, Bien Hoa, Da Nang, were all major entry points into South Vietnam...by airliner or ship. With the exception of the Tet offensive in 1968, combat normally occurred outside of those major bases.