Who is Radio Man, RTO Mann from The Killing Zone: My Life in the Vietnam War and what is their importance?

RTO Mann is Lt. Downs' radio officer, until at some point he completes his tour of duty in Vietnam and is sent home. He is described as thin and tall. Mann has been serving in Vietnam for many months and helps get Lt. Downs used to life in the jungle. He tells Downs to do things like stop and check for leeches, and put bug juice (repellent) on them. He is married and has a son he never has seen. At one point during a battle in the jungle he breaks down and fears he will be killed, but after some reassurance from Lt. Downs, he regains his composure. Among his idiosyncrasies is that he makes a pot of coffee any chance he gets, even on the battlefield.