Battle of Tannenberg
1914 CE.
Shown on the map at 53.750°, 20.500°.
The Battle of Tannenberg, also known as the Second Battle of Tannenberg, was fought between Russia and Germany between 26 and 30 August 1914, the first month of World War I. The battle resulted in the encirclement and the almost complete destruction of the Russian 2nd Army by the German 8th Army and the suicide of its commanding general, Alexander Samsonov. A series of follow-up battles (First Masurian Lakes) led to the ousting of the Russian 1st Army from East Prussia. The outcome brought considerable prestige to the German army commander, General Paul von Hindenburg, and his rising staff officer, General Erich Ludendorff. Although the battle actually took place near Allenstein (Olsztyn), Hindenburg named it after Tannenberg, 30 km (19 mi) to the west, in order to avenge the Teutonic Knights' defeat at the Battle of Grunwald 500 years earlier. The East Prussian campaign is particularly notable for fast rail movements by the German 8th Army, enabling them to concentrate against each of the two Russian armies in turn, first delaying the 1st Army and then destroying the 2nd before once again turning on the 1st days later.
Text from the Wikipedia article Battle of Tannenberg, licensed CC BY-SA 4.0.