First Battle of the Masurian Lakes

BelligerentsGermanyRussian EmpireCommanders and leadersPaul von Hindenburg
Erich Ludendorff
August von MackensenPaul von RennenkampfUnits involved8th Army1st Army
10th ArmyStrengthTotal 244,391 men
7 military corps
1,146 guns
400 machine gunsTotal 553,937 men
1,673 guns
960 machine guns:
1st army:
306,470 men,
924 guns
395 machine guns
10th army:
247,467 men
749 guns
565 machine gunsCasualties and losses

German official medical reports (1 - 30.09.1914):
1,555 KIA,
10,412 WIA,
1,552 MIA,
Total 13,519
Lost:
17 guns
17 machine guns

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10,000 killed, wounded and missing
Other Estimate:
40,000 killed and wounded

100,000–125,000 killed, wounded and captured,
Lost:
162 guns
174 machine guns

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70,000 killed and wounded,
30,000–45,000 prisoners

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Russian Estimate:
about 60,000 died, wounded and prisoners
Staff of the Russian NW front: 100,000 men, including 50,000 prisoners

The First Battle of the Masurian Lakes was a German offensive in the Eastern Front 2–16 September 1914, during the Russian invasion of East Prussia. It took place only days after the Battle of Tannenberg where the German 8th Army encircled and destroyed the Russian 2nd Army. Using the rapid movements aided by the East Prussian railway network, the 8th Army reformed in front of the spread-out Russian 1st Army and pushed it back across its entire front, eventually ejecting it from Germany. Further progress was hampered by the arrival of the Russian 10th Army on the Germans' right flank.

By the conclusion of the battle, the Imperial German Army had destroyed the 2nd Army and shattered the First in a series of actions over only a few weeks. However, Russia had the largest army in the world, so the Russian army very quickly restored its losses in manpower, and after a couple of weeks the Russians launched a new offensive in East Prussia.