Battle of Tannenberg, 26-31 August 1914
Battle of the First World War; a crushing German victory over the Russians invading East Prussia. After a series of minor defeats against the Russians, the Germans placed General Paul von Hindenburg in command of the eastern front, with General Erich Ludendorff as his chief of staff, and on 22 August, before leaving for the east, Ludendorff put in place a plan to attack the Russian Second Army under General Alexander Samsonov, ignoring for the moment the Russian First Army. On 24 August the Russian advance was halted at the battle of Orlau-Frankenau by the German XX Corps, which then withdrew to Tannenberg. Unbelievably, the Russians were using uncoded radio transmissions, and by this point the Germans knew exactly where the Russian troops were. On 26 August the battle started. The German XCII and I Reserve Corps pushed back the Russian right, the I Corps their left, and the XX Corps attacked their centre. On the third day (29 August), the I Corp completed the encirclement of the Russian army, after which Samsonov was never heard from again, and his army disintegrated. By 31 August the battle was over. The Russians had lost 125,000 men, ten times the German losses. This, combined with the defeat of the Russian First Army at the First Battle of the Masurian Lakes (9-14 September), ended any immediate threat from the Russians and provided a great boost to morale in Germany
The Warlords: The Campaigns of Hindenburg and Ludendorff, How to cite this article: Rickard, J. (7 February 2001), Battle of Tannenberg, 26-31 August 1914, http://www.historyofwar.org/articles/battles_tannenberg.html
John Lee, Weidenfeld & Nicholson, 2005, 224 pages. A good account of the rise of Hindenburg and Ludendorff from command on the eastern front against Russia, to overall control of the war and eventually to the virtual dictatorship of Germany.