First Battle of the Masurian Lakes, 9-14 September 1914, (East Prussia)
Second major Russian defeat of the First World War. After the defeat of the Russian Second Army at Tannenburg, the Germans were free to turn on the First Army, under Rennenkampf. However, unlike at Tannenburg, the Germans, despite now outnumbering the Russians, were unable to encircle them in the broken terrain of the Masurian Lake lands, and Rennenkampf was able to extract his army intact, and even launch his own counterattack on 25 September which regained much of the land lost during the battle. However, the result of the two Russian defeats was to remove any threat to East Prussia.
The Warlords: The Campaigns of Hindenburg and Ludendorff, How to cite this article: Rickard, J. (15 March 2001 ), First Battle of the Masurian Lakes, 9-14 September 1914, http://www.historyofwar.org/articles/battles_masurian.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.