This is an illustration of the major battles of WWI. Shown on this image are the Battle of Tannenberg, Battle of Marne, Battle of Ypres (1st), (3rd) Battle of Ypres, Battle of Gallipoli, Battle of Verdun, Battle of the Somme, and the Battle of Caporetto.
Trench warfare - This is a form of land warfare using occupied fighting lines consisting largely of trenches, in which troops are significantly protected from the enemy's small arms fire and are substantially sheltered from artillery. It has become a byword for stalemate, attrition and futility in conflict. Trench warfare occurred when a revolution in firepower was not matched by similar advances in mobility, resulting in a grueling form of warfare in which the defender held the advantage.