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?
2nd Army Corps (Russian Empire) The 2nd Army Corps (Russian: 2-й армейский корпус ) was a formation in the Imperial Russian Army that was active during World War I. It was headquartered in Grodno prior to the outbreak of the war, and took part in the Battle of Tannenberg in August 1914.
First Battle of the Isonzo The First Battle of the Isonzo was fought between the Armies of Italy and Austria-Hungary on the Italian Front in World War I, between 23 June and 7 July 1915.