The Swedish army was now reinforced by ten thousand Hessians, which the Landgrave of Casse commanded. Gustavus Adolphus had already invested Königstein; Kostheim and Flörsheim surrendered after a short siege; he was in command of the Main; and transports were preparing with all speed at Höchst to carry his troops across the Rhine. These preparations filled the Elector of Mentz, Anselm Casimir, with consternation; and he no longer doubted but that the storm of war would next fall upon him. As a partisan of the Emperor, and one of the most active members of the League, he could expect no better treatment than his confederates, the Bishops of Würtzburg and Bamberg, had already experienced. The situation of his territories upon the Rhine made it necessary for the enemy to secure them, while their fertility afforded an irresistible temptation to a necessitous army. Miscalculating his own strength and that of his adversaries, the Elector flattered himself that he was able to repel force by force, and weary out the valor of the Swedes by the strength of his fortresses. He ordered the fortifications of his capital to be repaired with all diligence, provided it with every necessary for sustaining a long siege, and received into the town a garrison of 2,000 Spaniards, under Don Philip de Sylva. To prevent the approach of the Swedish transports, he endeavored to close the mouth of the Main by driving piles and sinking large heaps of stones and vessels. He himself, however, accompanied by the Bishop of Worms, and carrying with him his most precious effects, took refuge in Cologne, and abandoned his capital and territories to the rapacity of a tyrannical garrison. But these preparations, which bespoke less of true courage than of weak and overweening confidence, did not prevent the Swedes from marching against Mentz and making serious preparations for an attack upon the city. While one body of their troops poured into the Rheingau, routed the Spaniards who remained there, and levied contributions on the inhabitants, another laid the Roman Catholic towns in Westerwald and Wetterau under similar contributions. The main army had encamped at Cassel, opposite Mentz; and Bernhard, Duke of Weimar, made himself master of the Mäusethurm and the Castle of Ehrenfels, on the other side of the Rhine. Gustavus was now actively preparing to cross the river and to blockade the town on the land side, when the movements of Tilly in Franconia suddenly called him from the siege, and obtained for the Elector a short repose.