The Russian invasion of Eastern Prussia occurred on the Eastern Front of World War One. The offensive was a means of diverting German troops from the Western Front to the Eastern Front of the Great War, thus providing indirect support to the British and French forces. In the end, despite the fact that they had superiority in numbers over the Germans, the Russians were defeated in the battles of Tannenberg and Masurian Lakes.
The Russian Army was a huge beast. Even though the reservoir for conscription was largely restricted to the Russian Christian population, and multifarious reasons were justification for exemption, the empire was so huge that the standing army of 1.4 million would reach 5 million on mobilization. Their training had been rudimentary, concentrating on basic soldierly skills. Yet in some areas, the Russian Army was surprisingly innovative, with a large Imperial Air Service and much experimentation ongoing into the possibilities of armored cars. Yet many of these new weapons were not yet operational.
The German Army on the Eastern Front would always be outnumbered, but would also always be superior in training, leadership, supply and weaponry. Its core was the belief that conscripts, if well trained, equipped and led, would provide adequate front-line troops in larger numbers than those of other belligerents that used conscript reservists only for secondary or garrison duties.
Germany declared war on Russia following the Russian general mobilization. It is ironic that Austria-Hungary, which had declared war on Serbia, only belatedly declared war on Russia. Romania and Bulgaria had resolved to stay out of the war, but the Eastern Front which was created was still immense, stretching some 1,000 miles. The distances involved in military operations were vast, forcing a dependence on railways. For the Germans and Austrians, blessed with superb railway networks, this was not a problem, but over the border in Russia the system was far more ramshackle.
The Russian Commander-in-Chief was Grand Duke Nicholas, the Tsar’s brother. The Russian First and Second Armies faced the German Eighth Army. The plan was simple: the First Army, commanded by General Paul von Rennenkampf, would advance into East Prussia north of the Masurian Lakes, while the Second Army, under General Alexander Samsonov, would advance south of the lakes. The whole offensive would be coordinated, at least in theory, by General Yakov Zhilinsky, although communications would prove dire.
The internal strifes that had gone on within the army before 1914 resulted in an absence of a real plan for war: troops were frittered away between different operations, since there was no single authority to impose its will on the army. Moreover, when war broke out, that single authority did not emerge even when an ostensible supreme command (Stavka) was appointed. Stavka, in the early phase of the war, was a helpless victim of circumstances. Real power was held by the separate army groups, and not by Stavka itself, which was scraped together at the last moment.
Rennenkampf began his advance, pushing aside resistance from the German Eighth Army, commanded by Lieutenant General Max von Prittwitz, during heavy fighting at Gumbinnen. The Germans were forced to retreat by weight of numbers. Rennenkampf followed up tardily, first reorganizing his units for a couple of days and then advancing far too slowly, thereby allowing the Germans to break contact with his forces. This might not have mattered much, as Prittwitz was already panicking, concerned as he was by the threat to his communications from Samsonov’s Second Army which he knew was poised to begin crossing the Prussian border from Russian Poland.
A desperate Prittwitz resolved to retreat all the way back to the Vistula River, thereby abandoning the whole of East Prussia. This was far too much for the German Commander-in-Chief Helmuth von Moltke, who immediately dismissed the hapless Prittwitz and replaced him with General Paul von Hindenburg. He was accompanied by his Chief of Staff, Major General Erich von Ludendorff, a far more mercurial character. They would prove to be one of the great command teams of the Great War.
When Hindenburg took command he was immediately offered a plan of action by the Eighth Army staff officer Colonel Max Hoffmann. Hoffmann suggested leaving only screening forces in front of the slow-moving First Army and utilizing the efficiency of the superb German railway system to switch the bulk of the Eighth Army to challenge Samsonov’s Second Army head on as it marched north and northwest into East Prussia. The plan was to defeat the superior Russian forces in detail, switching the Eighth Army from front to front, allowing it to fight in turn first the Second Army and then the First Army.
Whatever Samsonov thought was happening, reality burst upon him only in stages: first his left wing was attacked, then his right. The whole of the Second Army was cut off, at first only by a weak German force, but as the Germans pressed on the Russians found themselves effectively surrounded by a ring of steel, with no chance of escape. The Battle of Tannenberg, as it would come to be known, was an unmitigated disaster for the Russian Army. Soon the Russians had no option but to surrender.
Above all, Tannenberg mattered because of its propaganda effect: its impact on perceptions. Hindenburg requested the battle be so named in revenge for the defeat of the Teutonic Knights at the hands of the Poles at Tannenberg 500 years previously. Such symbols were important to the Prussian mentality. Furthermore, the impression it created, that of a decisive and historic success, helped obscure the absence of such a victory where it was actually wanted, in the west. The illusion of German military invincibility was fostered, not simply in the minds of the press-reading public but also in those responsible for the direction of policy itself.
Chastened by the destruction of the Second Army, Rennenkampf had suspended his advance and withdrawn to a more defensible line stretching from Königsberg in the north down to the Masurian Lakes to the south. The Germans concentrated on the left of his line and managed to break through. The Tenth Army was still forming up in Poland and so was unable to lend any assistance. Rennenkampf was forced into a humiliating retreat, falling back across the Prussian border he had crossed with so much hope less than a month before.
By the end of September the Russians were back along the river Niemen, minus over 250,000 dead, wounded or captured. Their sacrifice did, however, help France to survive. Five German divisions, rushed from the west in response to Prittwitz's panicky reports, arrived only after Tannenberg had shown they were not needed. They were immediately returned west, but arrived too late for the Battle of the Marne. Colonel Dupont, Head of French Intelligence, later said of the Russians that 'their debacle was one of the elements of our victory'.