Not one damned thing! WWI was one of this planets bloodiest conflicts. Usually entrenched troops were harder to dislodge and with the advent of many new weapons of war,ie machine gun, airplane, tank, flamethrower, poison gas etc taking your opponents trenches proved to be very costly. For the reasons mentioned above and add with them stupidity and stubbornness WWI proved to be a stagnant war with neither side moving forwards or backwards very much