This slow retreat continued from the 7th of December to Christmas Eve, and involved the surrender of a number of Polish towns, but it left the Russians in a strong position. They were able to entrench themselves so that every attack of the enemy was broken. The Germans tried hard. Von Hindenburg would have liked to enter Warsaw on Christmas. The citizens heard day and night the sound of the cannon, but they were entirely safe. The German attack was a failure. On the whole, the Grand Duke Nicholas had shown better strategy than the best of the German generals. Outnumbered from the very start, his tactics had been admirable. Twice he had saved Warsaw, and he was still threatening Cracow. The Russian armies were fighting with courage and efficiency, and were continually growing in numbers as the days went by. During the first weeks of 1915 while there were a number of attacks and counter-attacks both armies had come to the trench warfare, so familiar in France. The Germans in particular had constructed a most elaborate trench system, with underground rooms containing many of the ordinary comforts of life. Toward the end of the month the Russians began to move in East Prussia in the north and also far south in the Bukovina. The object of these movements was probably to prevent von Hindenburg from releasing forces on the west. Russia was still terribly weak in equipment and was not ready for a serious advance. An attack on sacred East Prussia would stir up the Germans, while Hungary would be likewise disturbed by the advance on Bukovina. Von Hindenburg, however, was still full of the idea of capturing Warsaw. He had failed twice but the old Field Marshal was stubborn and moreover he knew well what the capture of Warsaw would mean to Russia, and so he tried again. The Russian front now followed the west bank of the Bzura for a few miles, changed to the eastern bank following the river until it met with the Rawka, from there a line of trenches passed south and east of Balinov and from there to Skiernievice. Von Mackensen concentrated a considerable army at Balinov and had on the 1st of February about a hundred and forty thousand men there. That night, with the usual artillery preparation, he moved from Balinov against the Russian position at the Borzymov Crest. The Germans lost heavily but drove forward into the enemy’s line, and by the 3d of February had almost made a breach in it. This point, however, could be readily reinforced and troops were hurried there from Warsaw in such force that on February 4th the German advance was checked. Von Mackensen had lost heavily, and by the time it was checked he had become so weak that his forces yielded quickly to the counter-attack and were flung back.