Russian mobilization was more rapid than Russia's allies could have hoped for and it wholly confounded the Germans. While the Battle of the Marne was still two weeks off Russian forces were sweeping west from the Niemen and approaching Koenigsberg, a second army was striking north from Warsaw. East Prussian populations were fleeing before the invaders and a German disaster seemed imminent. The genius of Hindenburg, who now appeared upon the eastern battle ground, saved the situation. Gathering in all his available forces and leaving the Russian army coming from the Niemen almost unopposed, he caught the Warsaw army in the swamps about the frontier in the last days of August and, thanks to his generalship and heavy artillery, destroyed a Russian army. Tannenberg was a great victory and it saved East Prussia. The Niemen army had to retreat rapidly to escape destruction. At the time, it was asserted that the Russian invasion had compelled the Germans to draw upon their western front to meet the thrust and thus to weaken their armies in advance of the decisive battle. This is not now believed to be true, but there is no doubt that it drew reserves who might otherwise have gone to the west or to the south. Tannenberg was a victory which filled the world with its splendor, but it merely disguised for the moment the far more considerable Austrian disaster to the south. One Austrian army had crossed the frontier and approached Lublin, another had advanced east from Lemberg. Upon the Lemberg army the full weight of the Russian thrust now fell and the army was promptly routed, driven through Lemberg and west of the San or across the Carpathians. The force that had approached Lublin was thus left in the air and succumbed to a series of disasters, which culminated in the terrible defeat of Rawa-Ruska. Meantime the Austrian troops, which had invaded Serbia were routed in the Battle of the Jedar, which preceded the other Austrian disasters and was, in fact, the first considerable triumph for the Allies in the whole war. AUSTRIAN PERIL Austria was now in dire straits and her whole military structure seemed on the point of crumbling. Russian armies flowed west through Galicia and approached Tarnow, Przemysl was isolated, tens of thousands of prisoners, innumerable guns and vast quantities of stores fell to the victors. While the great German attack upon France was failing, Russia seemed on the point of achieving against Germany's ally what Germany had failed to achieve against France.