Part of the problem: The Germans has a machinegun the 08/15 Maxim. The British had guns, not howitzers, and could not fire effectively against anything but the very most exposed German lines.
The British launched the attack to take pressure off the French at Verdun. That worked when they shelled the area for about two weeks. Alas, it was about the only thing that did work. Aside from the "nul ack funfsten" which worked terrifingly well.
Sir Douglas Haig changed the units battlefield reports to hide his complicity. He blamed his boss for it, and managed to move up.
Well, of course, it was an American invention :-)
My grandfather was there as member of the North Irish Horse. By then they were reduced to a leg outfit.