Interestingly, the trench war episodes during the Russo-Japanese war (siege of Port Arthur) were a good demo-version of the Western Front ten years later.

The observers from the West were very clear in their warnings towards the General Staff back home that the combination of barbed wire and rapid firepower was massively deadly and led to stalemates. Also, that cavalry was becoming outright obsolete in such conditions.

They were mostly ignored because they were young.