The one thing they did not learn was that frontal assaults on heavily fortified positions was not feasible, because the thinking of the time was that it was "only" the Russians and Japanese. I have read dispatches by British Army officers who were attached to the Japanese Army in the siege of Port Arthur and their statements were very condesending. One Captain even went so far as to say only the Japanese would have such terrible casualties, as a proper "European" army would have stormed the works. That is the attitude which caused such terrible carnage on the western front. It was only after the "Generals", and i use this term loosely, had wasted most of a generation of valiant men, did they try to find ways around trench warfare. The Germans with Stosstruppen infiltration, and whirlwind artillery bombardments in support. The Allies on technical means, aka, tanks. When if they would have taken the lessons to heart instead of brushing it off as a squabble between an Asiatic power and a third rate European power, maybe the first world war would have been less bloody or avoided all together.
Cheers Thorgrimm