High Quality Content by WIKIPEDIA articles! The Battle of Tannenberg was an engagement between the Russian Empire and the German Empire in the first days of World War I. It was fought by the Russian First and Second Armies against the German Eighth Army between 26 August and 30 August 1914. The battle resulted in the almost complete destruction of the Russian Second Army. A series of follow-up battles destroyed the majority of the First Army as well, and kept the Russians off-balance until the spring of 1915. The battle is notable particularly for a number of rapid movements of complete German corps by train, allowing a single German army to concentrate forces against each Russian army in turn.