The First Battle of the Masurian Lakes was a major battle of World War I which was fought on the Eastern Front in 1914. Just days after the Russians' crushing defeat at the Battle of Tannenberg, the German 8th Army pushed the scattered Russian 1st Army out of East Prussia, preventing the Russians from launching any new offensives until the spring of 1915.
Background[]
In the autumn of 1914, the Russian First (under Paul von Rennenkampf) and Second Armies (under Alexander Samsonov) invaded German East Prussia, forcing the German 8th Army to retreat towards Koenigsberg, and allowing the Cossacks to pillage and rape across the East Prussian countryside. However, Imperial Russian Army Chief of Staff Yakov Zhilinsky clumsily separated the two Russian armies and ordered them to advance across nearly impassable terrain as part of a hastily-organized early offensive launched at the behest of the French, who feared that a Russian delay would result in their defeat on the Western Front. The German general Paul von Hindenburg was thus able to quickly surround the Russian 2nd Army as it marched over difficult, hilly terrain, and the 2nd Army was surrounded and destroyed at the Battle of Tannenberg on 26-30 August 1914. Rennenkampf ordered his men to pull back upon hearing of this disaster, and his 300,000-strong army, the Russian 10th Army, and the remnants of the 2nd Army formed a new line between the Deime Valley in the north and Angerburg (Wegorzewo) in the south. Hindenburg tasked the German 8th Army with clearing East Prussia of the Russian invaders, after which the 8th Army would advance on Warsaw in Russian Poland. The smaller German army attacked the larger, yet poorly-coordinated and scattered Russian army among the Masurian Lakes, threatening to outflank the Russians. A major Russian counterattack failed in the face of hurricane artillery and machine-gun fire, and, by midnight on 11 September, the Russian 2nd Corps was retreating across the Goldapa River, and the Germans threatened the Russians' left flank. Rennenkampf was forced to order a withdrawal on 11 September, and the 1st Army's stubborn resistance fatigued its soldiers and resulted in heavy Russian losses. The 1st Army withdrew from East Prussia in a panicked retreat, and attempts by other Russian corps to protect the 1st Army's retreat were unsuccessful. Rennenkampf was ultimately able to restore control of his troops at Kovno (Kaunas), escaping encirclement in spite of his defeat. Grand Duke Nikolai dismissed Zhilinsky as Chief of Staff and replaced him with Nikolai Ruzsky, and he ordered the Russian 5th Army north from Eastern Galicia to defend Warsaw. On 15 September, the Germans formed the German 9th Army to protect Silesia. However, the Germans' transfer of troops from the west to fight off the Russians resulted in the failure of their offensive at the First Battle of the Marne, and, from 25 to 28 September, a Russian counterattack recaptured much of their lost territory.