At first the Russians repelled the attack on the causeway, but on November 19th the Russians broke and were compelled to fall back. Over the causeway, then, the German troops were rushed in great numbers, splitting the Russian army into two parts; one on the south surrounding Lodz, and the other running east of Brezin on to the Vistula. The Russian army around Lodz was assailed on the front flank and rear. It looked like an overwhelming defeat for the Russian army. At the very last moment possible, Russian reinforcements appeared--a body of Siberians from the direction of Warsaw. They were thrown at once into the battle and succeeded in re-establishing the Russian line. This left about ninety thousand Germans almost entirely surrounded, as if they were in a huge sack. Ruzsky tried his best to close the mouth of the sack, but he was unsuccessful. The fighting was terrific, but by the 26th the Germans in the sack had escaped. The Germans were continually receiving reinforcements and still largely outnumbered the Russians. Von Hindenburg therefore determined on a new assault. The German left wing was now far in front of the Russian city of Lodz, one of the most important of the Polish cities. The population was about half a million. Such a place was a constant danger, for it was the foundation of a Russian salient. When the German movement began the Russian general, perceiving how difficult it would have been to hold the city, deliberately withdrew, and on December 6th the Germans entered Lodz without opposition. The retreat relieved the Russians of a great embarrassment. Its capture was considered in Germany as a great German victory, and at this time von Hindenburg seems to have felt that he had control of the situation. His movement, to be sure, had not interfered with the Russian advance on Cracow, but Warsaw must have seemed to him almost in his power. He therefore concentrated his forces for a blow at Warsaw. His first new movement was directed at the Russian right wing, which was then north of the Bzura River and east of Lowicz. He also directed the German forces in East Prussia to advance and attempted to cut the main railway line between Warsaw and Petrograd. If this attempt had been successful it would have been a highly serious matter for the Russians. The Russians, however, defeated it, and drove the enemy back to the East Prussian border. The movement against the Russian right wing was more successful, and the Russians fell back slowly. This was not because they were defeated in battle, but because the difficult weather interfered with communications. There had been a thaw, and the whole country was waterlogged. The Grand Duke was willing that the Germans should fight in the mud.