Question: The 2nd Army Corps took part in the Battle of Tannenberg,  fought between Russia and Germany from 26–30 August 1914, during the first month of what war?
Sentence (from "Battle of Tannenberg"): The battle is particularly notable for fast rail movements by the Germans, enabling them to concentrate against each of the two Russian armies in turn, and also for the failure of the Russians to encode their radio messages.
Relevant evidence: No