From 1965 to 1971 the United States Marines in Vietnam ran a small, little-known operation called the "Combined Action Program." In many ways what CAP did was similar to what was done by the US Army Special Forces, the famous Green Berets, except the Marines concentrated most of their effort in the heavily populated coastal lowlands rather than the sparcely populated highlands. Most CAP units consisted of a Marine rifle squad and US Navy Medical Corpsman, and a Vietnamese Popular Forces platoon (roughly equivilant to the US National Guard, but with less prior training and poorer equipment), and were commanded by a Marine sergeant or corporal. Combined Action Platoons were frequently semi-isolated and usually independent units. There has been very little written about them. The one in The Night Fighters is loosely based on the combat-outpost type of CAP I served in during the spring and summer of 1966. To my knowledge, this was the first fictional treatment of a CAP.

KNIVES IN THE NIGHT introduces the Marines of CAP Tango Niner and the Popular Forces of Bun Hou village, somewhere deep in "Indian Country." The Marines and Vietnamese soon find themselves pitted against Major Nghu, a sadistic North Vietnamese Army officer dedicated to wiping out the Marines and subjugating the South Vietnamese peasants.