The movement therefore began, and by November 12th, the Russian cavalry had taken Miechow on the German frontier, about twenty miles north of Cracow. Its main forces were still eighty miles to the east. About this time Grand Duke Nicholas perceived that von Hindenburg was preparing a counter stroke. He had retreated north, and then, by means of his railways, was gathering a large army at Thorn. Large reinforcements were sent him, some from the western front, giving him a total of about eight hundred thousand men. In his retreat from Warsaw, while he had destroyed all roads and railways in the south and west, he had carefully preserved those of the north already planning to use them in another movement. He now was beginning an advance, once again, against Warsaw. On account of the roads he perceived that it would be difficult for the Russians to obtain reinforcements. Von Hindenburg had with him as Chief of Staff General von Ludendorff, one of the cleverest staff officers in the German army, and General von Mackensen, a commander of almost equal repute. The Russian army in the north had been pretty well scattered. The Russian forces were now holding a front of nearly a thousand miles, with about two million men. The Russian right center, which now protected Warsaw from the new attack could hardly number more than two hundred thousand men. Von Hindenburg’s aim was Warsaw only, and did not affect directly the Russian advance to Cracow, which was still going on. Indeed, by the end of the first week in December, General Dmitrieff had cavalry in the suburbs of Cracow, and his main force was on the line of the River Rava about twelve miles away. Cracow had been strongly fortified, and much entrenching had been done in a wide circle around the city. The German plan was to use its field army in Cracow’s defense rather than a garrison. Two separate forces were used; one moving southwest of Cracow along the Carpathian hills, struck directly at Ivanov’s left; the other, operating from Hungary, threatened the Russian rear. These two divisions struck at the same time and the Russians found it necessary to fight rear actions as they moved forward. They were doing this with reasonable success and working their way toward Cracow, when, on the 12th of December, the Austrian forces working from Hungary carried the Dukla Pass. This meant that the Austrians would be able to pour troops down into the rear of the Russian advance, and the Russian army would be cut off. Dmitrieff, therefore, fell rapidly back, until the opening of the Dukla Pass was in front of his line, and the Russian army was once more safe.