The Battle of Tannenberg was fought between Russia and Germany between 23 and 30 August 1914, the first month of World War I. The battle resulted in the almost complete destruction of the Russian Second Army. Although the battle actually took place near Allenstein, Hindenburg re-named it after Tannenberg 30 km to the west, in order to overshadow the Teutonic Knight`sdefeat at the First Battle of Tannenberg 500 years earlier.

The battle is particularly notable for fast rail movements by the German Eighth Army, which are referred here to as COUP DE DÉS.