[@TwelveOf8]I likely don't have the same level of experience as Lady Selune on the subject, but I can still offer helpful explanations and links to online articles for additional reading. To answer your problem of not knowing how the army worked at this time: Basically somewhere between WW2 and the modern day. Some of the ranks of WW2 were gone, but some of the weapons and command structure were the same, and despite the creation of the Air Force, the Army still had plenty of its own air support at this time. This roleplay, however, is going to focus more on the jungle and forest small unit combat of the war, rather than general military life, so the most you'll need to know is where ranks fall in the linear chain of command, and the Vietnam-era Phonetic alphabet for objective names and the like. Wikipedia has plenty of stuff of use in this case, including a page listing all the firearms and weapons used by the various militaries involved in the conflict.