The word "code" in the military is for communication via radio, etc. Such as Bravo 26, or Mike 1 Alpha. The military uses the "phonetic alphabet" to avoid confusion over the radio. The letter "B" can sound like the letter "C' or "D" or "E", so we use Bravo, Charley, Delta, or Echo. The Viet Cong (VC, the "guerilla" enemy) or the North Vietnamese Army (NVA, the regular army enemy) were referred to as "Victor Charley" and "November Victor Alpha." The phonetic alphabet then breaks down into far more complicated codes, to avoid detection by enemy personnel. Those enter the category of Military Intelligence/Communications. If your question is about military operations in the Vietnam War, there's a list of nearly a hundred of them. See; Category: Battles and Operations of the Vietnam War.