German mobilization earmarked a single army, the Eighth, to defend their eastern frontier. Two Russian armies invaded East Prussia earlier than expected, the Eighth Army commanders panicked and were fired by OHL, Oberste Heeresleitung, German Supreme Headquarters. OHL assigned Ludendorff as the new chief of staff, while the War Cabinet chose a retired general, Paul von Hindenburg, as commander. They first met on their private train heading east. They agreed that they must annihilate the nearest Russian army before they tackled the second. On arrival, they discovered that General Max Hoffmann had already shifted much of the 8th Army by rail to the south to do just that, in an amazing feat of logistical planning. Nine days later the Eighth Army surrounded most of a Russian army at Tannenberg, taking 92,000 prisoners in one of the great victories in German history. Twice during the battle Ludendorff wanted to break off, fearing that the second Russian army was about to strike their rear, but Hindenburg held firm.