Battle of Verdun
The French commander, Marshall Philippe Pétain, used a system of rotation by which every division in France fought for a short time at Verdun.  After the battle the landscape was left as one of the worst battlegrounds on all of France, filled with craters of the artillery, the trenches, the odor left by the dead, etc.  During the battle the chief of the German General Staff, Erich Von Falkenhayn, was relieved from duty and sent to lead a joint Austrian, German and Bulgarian attack on Romania, leaving Paul Von Hindenburg as Chief of Staff.