The Grand Duke knew that while Brussilov advanced again through Galicia he must protect Brussilov's flank, so that the Germans could not interfere with his movements. In order to do this he must hold the Germans who had retreated towards the Warta by means of armies A, B, and C. If fortune favoured him he might, by means of the army A, roll up the left flank of the Germans, and hem them in between C and his fourth army, D, which was now marching south-east towards Cracow. He therefore hastened the advance of his troops all along the line. Army A advanced along the Vistula towards Thorn, and the cavalry screen of Cossacks, riding hard, was not twenty miles from that fortress on 9th November. Army B struck at the Warta in the neighbourhood of Kolo, and on 10th November its vanguard was actually across the German frontier, and had cut the railway from Posen to Cracow. Meanwhile Army C was striking at the Upper Warta, while Army D was pushing south-east. By 12th November the cavalry of this fourth army had got within twenty miles north of Cracow. While these movements were going on Brussilov was pushing westward once more, and had already reached and reoccupied the main passes of the Western Carpathians. Everything was going well, and many people in this country fully believed that the Russians would be in Cracow before long. But wiser folks wondered what new move von Hindenburg was about to make. It was not likely that the Germans would sit still under the terribly rough handling which they had recently received. They had lost very heavily, and they had been beaten back to their frontier, but they were still full of fight. On 13th November it was evident that they were going to make a very powerful counter-attack. Let me remind you of two facts which it is important that you should remember. The first is, that along the Polish frontier the Germans possess a network of railways which enable them to move troops from north to south very rapidly; the second is, that though the Germans had devastated much of Poland they had kept the roads and railways intact in the northern quarter of the country. As soon as von Hindenburg had withdrawn his left and centre behind his own frontier, he put his troops into trains, and hurried them northward to the neighbourhood of Thorn, where he had large reserves. Some of these reserves came from Germany, and some were brought from the Western front. Altogether he gathered in an astonishingly brief time a striking force of about 800,000 men, and behind them he had many thousands more. He now began to push eastward on a forty-mile front between the Warta and the Lower Vistula towards Warsaw once more. [Illustration]