What was "no man's land" during World War I?

During World War I, the area between the entrenched armies of the Allied and Axis armies in Europe was commonly known as "no man's land." The exact location of this area constantly changed as the war progressed.

The exact size of this small area varied depending on the location of soldiers on the front lines. At its widest, no man's land stretched to about half a mile. In other areas, however, it was merely a few dozen yards. Because both sides were so close to their enemies at this point, it became the site of most of the violent activity during the war.