World War 1
The battles of Tannenberg and the Masurian Lakes
East Prussia,(Germany that time)
Russian plans for the start of the war called for simultaneous invasions of Austrian Galicia and East Prussia. Although Russia's initial advance into Galicia was largely successful, it was driven back from East Prussia by Hindenburg and Ludendorff at the battles of Tannenberg and the Masurian Lakes in August and September 1914.