Re: In conjunction with Bowser's post....
That was early on. The "strategic hamlet" idea was akin to moving Native Americans onto urban reservations. It was abandoned very early in the war.
I don't think Captain Medina used the term "free fire zone", I did because it describes the situation. He was alleged to have said that everyone in the My Lai villages was VC. The usual body counts were important, and anyone dead was considered a hostile.
I do know that "free fire zone" was used in areas deemed to be rife with VC and NVA without leaflets being dropped. Units moving into those areas were instructed that everyone was a hostile until proven otherwise. Maps were issued with large areas so designated. One didn't protest the designation of an area as a "free fire zone" twice.