Russian invasion of East Prussia (1914)

East Prussian Campaign
Part of the Eastern Front of World War I
Eastern Front, 17–23 August 1914.
Date 17 August – 14 September 1914 Location East Prussia Result German victory
Belligerents
German Empire	Russian Empire
Commanders and leaders
Paul von Hindenburg Erich Ludendorff Maximilian von Prittwitz	Paul von Rennenkampf Alexander Samsonov † Yakov Zhilinskiy
Units involved
VIII Army	I Army II Army X Army
Strength
Total 250,000 men another estimate: 135,000	Total more than 800,000 men another estimate: 650,000
Casualties and losses
Total about 37,000 or 67,000 men: (Stallupönen - 1,300; Gumbinnen -14,600; Tannenberg - 12,000; Masurian lakes - 10,000 or 40,000)	in 4 main battles more than 320,000 men: (Stallupönen - 7,500; Gumbinnen - 19,000; Tannenberg - 170,000; Masurian lakes - 125,000) Another estimate: more than 300,000

Total 250,000 men

Total more than 800,000 men

in 4 main battles more than 320,000 men: (Stallupönen - 7,500; Gumbinnen - 19,000; Tannenberg - 170,000; Masurian lakes - 125,000)

The Russian invasion of East Prussia occurred during the First World War, lasting from August to September 1914. As well as being the natural course for the Russian Empire to take upon the declaration of war with Germany, it was also an attempt to focus the German armed forces on the Eastern Front, as opposed to the Western Front. Despite having an overwhelming superiority over the Germans in numbers, the invading Russian armies remained separated and were defeated in the battles of Tannenberg and the Masurian Lakes.

German strategy vis-à-vis Russia was defensive from 1888 onward, when the Chief of the German General Staff, Helmuth von Moltke, abandoned the concept of a decisive offensive into Russian territory and began to consider defensive options. According to German intelligence estimates, the railway network in Poland limited the Russians to three options: a purely defensive posture against Germany, an offensive down the Vistula straight towards Berlin or an invasion of East Prussia with two armies, one from the Narew and one from the Niemen. French political pressure blocked the first option, while the second option was militarily unsound, leaving the third option as the most likely Russian course of action.

In 1894 Alfred von Schlieffen, then Chief of the General Staff, war-gamed a scenario that corresponded to the Battle of Tannenberg in 1914. With the Russian Niemen army having overrun half of East Prussia, the German commander in the exercise exploited the separation between the Russian Narew and Niemen armies to mass his troops against the right flank of the Narew army and destroy the whole force. In the exercise critique Schlieffen said the Germans could easily just establish a defensive line behind the Vistula, but when the opportunity to destroy an entire Russian army was available, it should be taken.

...
Wikipedia