What are Vietnams three cores?

Answer 1

There were four corps; officially called Military Regions I, II, III, and IV. MR-1 covered Da Nang up to the DMZ, and is often referred to as "I Corps." II Corps (MR-2) was the largest and covered the Central Highlands (containing Pleiku and Ahn Khe). III Corps was the most important and had the bulk of the US units surrounding it, the capital; Saigon. Below Saigon was the Mekong Delta...IV Corps...swamps and muddy canals, mud and more canals...and incredibly humid and hot. IV Corps was VC country, probably no one ever saw an NVA there. III Corps had so many allied forces within it, units kept bumping into each other when operating in the field. II Corps was the beginning of NVA country, rarely were there any VC units there...and a fairly dangerous place; the NVA seldom ran; they held their ground. I Corps was simply "Hot" (dangerous); a contested place between the NVA and US units.