Russia's army was larger on paper; Germany concentrated and encircled it.
Quick answer
Germany won a decisive victory at Tannenberg in the last days of August 1914, when the German Eighth Army surrounded and destroyed an entire Russian field army in East Prussia. Around 90,000 Russians were taken prisoner for comparatively slight1 German losses; it was one of the most complete victories of the First World War.
In the last days of August 1914, in the lakes and forests of East Prussia, the German Eighth Army surrounded and destroyed an entire Russian field army. Around 90,000 Russians were taken prisoner and tens of thousands more killed or wounded, while German losses were comparatively slight. Tannenberg was one of the most complete victories of the First World War, and it made national heroes of the German commanders.
Two Russian armies invade East Prussia
When war broke out, Russia invaded German East Prussia faster than expected, sending in two armies: Rennenkampf's First Army from the east2 and Samsonov's Second Army from the south. The outnumbered German Eighth Army fell back, and its command was handed to Paul von Hindenburg3 with Erich Ludendorff as his chief of staff, guided by the planning of staff officer Max Hoffmann.
Paul von Hindenburg (second from left), commander of the Eighth Army, with his staff over a map on 28 August 1914, in the middle of the battle. Public domain
Turning on the southern army
The Germans knew, partly from intercepted Russian radio messages sent in clear4, that the two Russian armies were not cooperating and a wide gap lay between them. Leaving only a screen against Rennenkampf, they used their railways to shift the bulk of the Eighth Army south3 to concentrate against Samsonov's Second Army alone.
US Military Academy map of East Prussia, 23 to 26 August 1914: the Eighth Army shifts south against Samsonov while only a screen faces Rennenkampf in the north east. Public domain
A whole army marched into East Prussia and never marched out.
The encirclement
In several days of fighting around Tannenberg, the Germans held Samsonov's centre and drove hard around both his flanks. The Russian wings collapsed, and the German pincers closed behind the Second Army1, trapping its centre in the forests and lakes. Cut off and disintegrating, the encircled Russian corps were destroyed or forced to surrender.
German infantry pushing through Ortelsburg on 28 August 1914, as the eastern arm of the pincer closed behind the Russian Second Army. An illustration by Georg Carl Koch from a German war history published in 1919. Public domain
A shattered army and a legend
Samsonov's Second Army effectively ceased to exist; around 90,000 men were captured and tens of thousands killed or wounded. Samsonov, facing the ruin of his army, took his own life.5 The Germans named the victory Tannenberg after the medieval battle of 14104 fought nearby, turning a distant defeat into a symbolic revenge, and Hindenburg and Ludendorff rose to command the German war effort.
General Alexander Samsonov, commander of the Russian Second Army, in a newspaper portrait from about 1910, when he was governor general of Turkestan. Public domain
Frequently asked questions
When and where was the Battle of Tannenberg?
It was fought from 26 to 30 August 1914 in East Prussia1, around Hohenstein and Allenstein (today Olsztynek and Olsztyn, Poland), early in the First World War.
Who fought at Tannenberg and who won?
The German Eighth Army, under Hindenburg and Ludendorff, decisively defeated the Russian Second Army under Alexander Samsonov.
Why was the German victory so complete?
The two Russian armies failed to cooperate and sent radio orders in clear, which the Germans intercepted. Using their railways, the Germans concentrated against one Russian army and encircled it.
How many prisoners were taken?
The Germans captured around 90,000 Russian soldiers, and tens of thousands more were killed or wounded. German losses were far lighter.
Why is it called Tannenberg?
The Germans named it after the medieval Battle of Tannenberg (Grunwald) of 1410, fought nearby, where the Teutonic Knights were defeated. The 1914 name framed the victory as a symbolic revenge.
Sources and notes
Numbered notes in the text point to the works below.
