There is such a thing as a No Man's Land[0]. It can move, but if you don't dare cross it for even a few days, it's very real. It doesn't have to be glacial, and it currently exists in Ukraine. Breakout pockets don't mean it is porous everywhere.
[0] Ironically, the French phrase - from ground zero for the first known No Man's Land - is "le No Man's Land".
[0] Ironically, the French phrase - from ground zero for the first known No Man's Land - is "le No Man's Land".