I think another question though is, is an advance at such costs really worth it. The sheer level of brutality in a level of attrition means that the enemy kills his own troops pretty rapidly. This is especially true of the brits and their allies as that the British navy could typically keep the germans bottled up out of sheer numbers. I suppose if you trained marines well enough you could land them in small numbers perhaps with mabye a 2000 strong force of regulars to hold a basis. The main line could prolly break to meet them and if the naval bombardment and land was strong enough i think they could be defended well from the sea and supplied.

show them the left and then hit them with the right.

plus is a hill really worth all the men that are lost over it. Some hills yes and some hills no