Z̆iz̆ka now fully realised the impossibility of any compromise, and he prepared for a desperate struggle. His first intention had been to make the town of Pilsen the centre of his operations. From that town he had succeeded in driving out all the Catholics; and its fortifications were so strong that he hoped to make it good against all comers. But the growing strength of the fortress of Tabor led him to change his opinion; and he decided to withdraw from Pilsen, and to concentrate the whole force of his followers on the mountain from which they took their name. According to one account, the divisions in Pilsen itself were the main cause of this decision. Certainly some special explanation is needed of a step which proved, in one way, so disastrous to the reforming cause; for, during all the victories gained by the Utraquists, they were never able to recover this important fortress again. It was not, however, unconditionally that Z̆iz̆ka consented to abandon this position. He stipulated that he should be allowed to depart freely to Tabor, and that the granting of the Cup to the laity should be permitted in Pilsen. Wenceslaus of Duba, as leader of the Catholic forces, consented to the terms which Z̆iz̆ka proposed. Unfortunately, however, the doctrine that faith should not be kept with heretics had already taken deep root amongst the opponents of the Utraquists. While Z̆iz̆ka was still on his way from Pilsen to Tabor, he was attacked by Peter of Sternberg, at the head of a royalist force. Unprepared for this attack, and very inferior in the number of his forces, Z̆iz̆ka at first retreated before his enemies; but, finding himself compelled to fight, he took up his position on the bank of a fish-pond near the town of Sudomír. There, for the first time, he adopted the plan which became a special characteristic of his battles. He entrenched himself behind his baggage-waggons, over which his men fired at the advancing foe. The struggle was a fierce one; but at last the royalists were compelled to retreat, and Z̆iz̆ka went on in safety to Tabor.