During World War I, when infantry got tired advancing through No Man's Land, they took cover in shell craters, which were formed by the constant shelling of the battlefield. These craters provided some protection from enemy fire, but they were also dangerous, as they could be filled with water or gas. Soldiers also dug trenches and dugouts, which provided more substantial cover and protection for troops. Trench warfare was a defining characteristic of World War I, as soldiers would spend days, weeks, or even months in these makeshift shelters.
~~~Harsha~~~