Where is cod:ww1?
A game set in World War I would more than likely consist of a no-win situation. You start in the trench with nowhere to go but mill about in the trench or up on the battlefield. You could stay in the trench but then you'd be killed by the gas shells that would eventually come down. And it's not like you had a choice anyway, the commander will eventually tell you to go over the top where you'll either get hit by artillery, picked off by an enemy sniper, step on a landmine, or get mowed down by machine guns.
Not a fun game.