Battle of Tannenberg - German Consolidation of Eighth Army

German Consolidation of Eighth Army

Colonel Max Hoffmann, Prittwitz's deputy chief of operations, was well aware of the animosity between the Russian generals, and what it would likely mean for their plans. Guessing that the Russian armies would continue to operate separately, Hoffmann proposed moving almost all German forces not already in Königsberg's eastern defense line to the southwest, moving I Corps by train to the left of Samsonov's line, a distance of over 160 km (99 mi). The XVII Corps and I Reserve Corps, at the time south of I Corps, would be readied for a move further south to face the Russian VI Corps on Samsonov's right flank. The German 1st Cavalry Division would remain as a screen just south of the eastern edge of the Königsberg defenses, facing Rennenkampf's First Army. The eastern portion of the Königsberg defenses was the only portion fully manned, while the approaches from the south were entirely open.

In theory, the plan was extremely risky. If the First Army turned to the southwest instead of advancing directly westward toward Königsberg, they would appear on the Eighth Army's extreme left flank, allowing for either a counterattack against the Eighth, or alternately turn north toward Königsberg from the undefended south. However, Hoffmann was convinced of the soundness of his plan, both because he was aware of the animosity between the Russian generals, and also because of the Russian habit of transmitting the next day's orders over unencrypted radio communications. It appears the Russians had outrun their secure telegraph landlines, and were short of trained wireless telegraph operators and cryptographic equipment. This forced them to transmit their messages in the clear, and these were easily intercepted and translated by the Germans.

When Hindenburg and Ludendorff arrived on 23 August, they immediately stopped the retreat and put Hoffmann's plan into action. Since Prittwitz had already ordered the German troops to pull back via train, Ludendorff directed I Corps to alight near Deutsch-Eylau to cover the left flank of XX Corps, who had been in front of the Second Army since before the battle at Gumbinnen. Hoffmann had already issued similar orders, so little confusion resulted. The trap was being set.

Ludendorff also learned at this point that von Moltke had decided to take three corps and a cavalry division from the Western front and redeploy them to East Prussia. Ludendorff protested that they would arrive too late to have any effect, while at the same time weakening the German offensive through Belgium against France. However, von Moltke considered East Prussia too politically important to lose, and ignored Ludendorff's protests. Later, this movement of German forces would be seen as the final undoing of the Schlieffen Plan that demanded a considerable preponderance of local forces in a rapid encirclement and destruction of the French armies east of Paris as they were driven into the German anvil on the Franco-German border.