What impressed me the most: "Using home-brewed chemicals, they developed their pictures in the open air or in underground tunnels" if by chemicals to develop photos in open air means no need for a dark room, that is really not something easy to do with then available technology. It is basically Polaroid chemicals quality.
Also "The Americans denuded the landscape with chemicals to deny cover to the Viet Cong." means chemical weapons. How the US avoided international courts is something that should be better explained. Specially considering Iraqi invasion decades later alleging chemical weapons suspicions.
Some pictures look extremely noise and grain free for such old photos. Makes me think they are probably digitally enhanced or Vietnam chemicals were really first class quality.