No man's land
No man's land is land that is not part of any country. It may be unclaimed territory, or an area that is under dispute and not occupied because of fear or uncertainty.
In trench warfare, "no man's land" is the area between two enemy trenches. Each side tries to cross no man's land to reach the enemy's trenches and attack.
In World War I, when trench warfare was widely used, few attacking soldiers survived. No man's land was typically full of shell holes, dead bodies, and barbed wire, and raked by machine gun fire. Usually nobody was left alive there.