> I haven’t heard “dead man zone”

It's the space between trenches. I've been watching a WW1 chronological documentary where they use it, but it's also been said in various ways, as you say.

Said playlist: https://www.youtube.com/playlist?list=PLB2vhKMBjSxOb_127vxja...

Time Ghost makes awesome chrono documentaries for the major wars. And a ton of mini series on special topics.