On this day in 1914, the Russian 1st and 2nd Armies begin their advance into East Prussia, fulfilling Russia’s promise to its ally, France, to attack Germany from the east as soon as possible so as to divert German resources and relieve pressure on France during the opening weeks of the First World War.
The Russian 1st Army, commanded by Pavel Rennenkampf, and the 2nd Army, led by Aleksandr Samsonov, advanced in a two-pronged formation—separated by the Masurian Lakes, which stretched over 100 kilometers—aiming to eventually meet and pin the German 8th Army between them. For the Germans, the Russian advance came much sooner than expected; counting on Russia’s slow preparation in the east, they had sent the great bulk of their forces west to face France. By August 19, Rennenkampf’s 1st Army had advanced to Gumbinnen, where they faced the German 8th Army—commanded by General Maximilian von Prittwitz—in battle on the River Angerapp on August 20.
During the Battle of Gumbinnen, Prittwitz received an aerial reconnaissance report that Samsonov’s 2nd Russian Army had advanced to threaten the region and its capital city, Konigsberg (present-day Kaliningrad) as well. With his forces greatly outnumbered in the region, he panicked, ordering the 8th Army to fall back to the Vistula River, against the advice of his staff and against the previous orders of the chief of the German general staff, Helmuth von Moltke, who had told him "When the Russians come, not defense only, but offensive, offensive, offensive." From his headquarters at Koblenz, Moltke consulted with Prittwitz’s corps commanders and subsequently dismissed the general, replacing him with Paul von Hindenburg, a 67-year-old retired general of great stature. As Hindenburg’s chief of staff, he named Erich Ludendorff, the newly anointed hero of the capture of Belgium’s fortress city of Liege earlier that month.
Under this new leadership, and awaiting reinforcements summoned by Moltke from the Western Front, the German 8th Army prepared to face off against the Russians in East Prussia. Meanwhile, confusion reigned on the other side of the line, as the two advancing armies and their commanders, Rennenkampf and Samsonov, were cut off from each other and unable to successfully coordinate their attacks, despite enjoying numerical superiority over the Germans. This lack of communication would prove costly in the last week of August, when the Germans enveloped and devastated Samsonov’s 2nd Army, scoring what would be their greatest victory of the war on the Eastern Front in the Battle of Tannenberg. The battle elevated Hindenburg and Ludendorff to the status of national heroes in Germany. Their partnership, born in East Prussia in the opening weeks of the war, would eventually acquire mythic status, as the two men moved forward together at the heart of the German war effort, right up to the bitter end in 1918.