In late August 1914, the Eastern Front of World War One opened with what would be the most complete German victory of the war.
Russia’s planned invasion of East Prussia was ended before it could even begin by the encirclement and annihilation of the Russian Second Army at the Battle of Tannenberg.
Russia’s invading force was split into two Armies – the First Army under General Rennenkampf, which would invade north-east Prussia, and the Second Army under General Samsonov, which would concentrate its efforts further south.
These armies had mobilised and advanced much farther than the Germans had expected, and the bulk of the German armies were concentrated in the west against the French and the British.
The Russian plan involved a pincer movement, wherein the outnumbered German Eighth Army would be caught between the Russian 1st and 2nd armies.
Rennenkampf, having driven back the overconfident German General François in the Battle of Gumbinnen, paused to consolidate his forces.
German defeat saw the recall of François’ superior, Maximilian von Prittwitz. He was replaced by the markedly more aggressive combination of Paul von Hindenburg and Erich Ludendorff, and the pair immediately went on the offensive.
The German strategy
Ludendorff immediately concentrated six divisions against Samsonov’s advance, but this force was not as strong as the Russian Second Army, and would have made little headway on its own.
Here Ludendorff and Hindenberg took a calculated risk, and withdrew the rest of the German troops, aside from a light cavalry screen, from the Rennenkampf front, sending them against Samsonov’s wing.
By engaging Rennenkampf’s forces with cavalry troops in the north, the Germans hoped to delay the ability of the First Army to reinforce Samsonov’s Second Army in the southwest.
Once the armies were separated, Samsonov’s flanks would be crushed quickly, and the Russian centre completely surrounded. German forces would encircle the Russian Second Army.
The Russian generals were operating with insufficient communication lines. There was a particular problem imminently prior to the battle, as messages had to circumvent the great Masurian Lakes.
The Germans had also cracked Russian codes prior to the war, and while the Russians were aware of this, and there were some provisional new codes in place, new codebooks had not been fully distributed.
Zhilinskiy, the commander and co-ordinator of both Rennenkampf and Samsonov’s armies, and Rennenkampf each had a codebook, but Samsonov did not.
Many Russian messages were sent unencrypted, in the hope that they would not be intercepted, which allowed Ludendorff and Hindenberg to advance much more aggressively, as they frequently received intelligence on the messages that were sent between Rennenkampf and Samsonov.
Samsonov, unaware either of the German plan or that Rennenkampf had decided to pause, advanced unwittingly into the German trap.
The battle commences
After a brief delay German forces under General Francois initiated an attack on Samsonov’s left flank at Usdau.
The battle began on the 26 August, with François’ forces enjoying rapid success. Ludendorff and Hindenburg were not convinced that Rennenkampf would not intervene and so ordered that François wheel north, but François ignored this order.
The Germans then intercepted more missives, outlining more detailed marching plans and making it clear that Rennenkampf’s forces would and could not intervene if Samsonov’s army was engaged.
Even as the Germans surrounded the Second Army, Rennenkampf’s continued to march westward away from Samsonov.
Samsonov had eventually become aware of the peril of the situation by the evening of 28 August and ordered a general retreat, but it was too late, and the encirclement was completed by the 29 August.
On retreating, many Russian soldiers encountered German defensive lines cutting them off, and were either gunned down or taken prisoner.
The scale of the defeat
95,000 Russians troops were captured, with a further 78,000 estimated as killed or wounded, and of his original 150,000-strong army, only around 10,000 of Samsonov’s men escaped.
The Germans suffered fewer than 20,000 casualties and also captured over 300 guns. 60 trains were required to transport captured equipment to Germany.
Samsonov committed suicide after the battle, unable to face the disgrace of such a comprehensive defeat.
Hindenburg and Ludendorff were fêted as heroes back in Germany, with Hindenburg later replacing Erich von Falkenhayn as the German Chief of Staff.
Russia’s allies were shocked by the defeat, and it raised fears that a conquest of Russia may prove imminent.
The battle meant a deeper psychological victory for the Germans. At the Battle of Grunwald (known as the Battle of Tannenberg in German) in 1410, the Teutonic Knights had been routed by the Slavs.
Despite Hindenberg’s victory occurring around 30km away from the site of that defeat, he ensured that the battle would be known as the Battle of Tannenberg.
Header image credit: Russian prisoners of war at the Tilsit transit station after Tannenberg. Credit: Berlin Illustrated Newspaper / Commons.