Note: No man's land may also be understood as Terra nullius.
No man's land is a term for a land that is not occupied or more specifically land that is under dispute between parties that won't occupy it because of fear or uncertainty.
History
World War I
In World War I and other later wars which involved trench warfare, the term no man's land indicated the land between the trenches of the opposing armies. This land belonged to neither side; it was a neutral place on the battlefield.
No man's land was a very dangerous area because it usually provided none of the cover that trenches are designed to. However, soldiers were forced to venture into it when advancing, and stretcher bearers would need to traverse it if they were to bring in the wounded.
Cold War
During the Cold War no man's land was the territory close to the Iron Curtain. Officially the territory belonged to the Eastern Bloc countries, but over the entire Iron Curtain there were several wide tracts of uninhabited land, several hundred meters in length, containing watch towers, minefields and such.
See also: List of disputed or occupied territories
Art and entertainment
Place names