French soldiers build shelters at Saint-Agnant-sous-les-Cotes in eastern France in 1915. Shelling locations during sieges in WWI was a major strategy. Soldiers often built complex trenches, with many underground areas for shelter during times of being shelled. These shelters also led to the forward trenches, allowing troops under cover to move to and from key areas near the front. This was not uncommon in many areas during much of the stalemate of the battles at the Western front in WWI.