On top of what others have said I'm gonna throw in that we made new technology faster then we made new strategy's and we once starting fighting and tanks and gas and other weapons were used and it became a stalemate and going over the top and throwing bodies at the enemy is a tried and true method. We do see near the end of the war new strategy's used by German stormtroopers who used in infiltration tactics on weak parts of the allied line which would then pave the way for regular infantry to exploit the disruption in the allied lines.