But further the prosecution of the attack became more and more difficult. The withdrawal of General Debschitz had seriously reduced the working strength of the besieging force. There were only nine battalions for the exhausting service in the trenches. Specially serious was the heavy loss in pioneers, and two fresh companies had to be brought up from Strasburg. The bright moonlight illuminating the fields of snow far and wide made it impossible to proceed with the flying saps. Sap-rollers had to be used; the heads of the saps had to be protected by sandbags and the sides by gabions, while the earth for filling had often to be brought from a long distance in the rear. On the head of all this, on February 3rd, a thaw set in, and the water from the heights filled the trenches, so that all communication had to be carried on across the open ground. Torrents of rain damaged the finished works; the parapet of the first parallel gave way altogether in places, and the banquette was washed away. The bottomless tracks made the arming of the batteries unspeakably difficult, and the teams of the columns and field artillery had to be employed in bringing up the ammunition. Many guns had become useless by overheating, while the enemy understood, by rapidly running out their guns, firing, and then running them back again, how to interrupt the work. Not merely was it necessary to continue the shelling of the Perches during the night, but a brisk rifle fire had to be kept up against them. Only now and then did the batteries newly placed in the parallels succeed in entirely silencing the guns of Hautes Perches. Epaulments had to be erected against Fort Bellevue and the defences of the railway-station, and Fort des Barres resumed activity. That under such exertions and the abominable weather the health of the troops suffered severely, need not be said; the battalions could often only muster 300 men for duty. Meanwhile, however, the artillery of the attack had unquestionably become very much superior to that of the defence, and, in spite of every obstacle, the saps were pushed on to the edge of the ditch of Les Perches.