Gustavus Adolphus now conveyed his artillery and the greater part of his troops over the river, and laid siege to Oppenheim, which, after a brave resistance, was, on December 8, 1631, carried by storm. Five hundred Spaniards, who had so courageously defended the place, fell indiscriminately a sacrifice to the fury of the Swedes. The crossing of the Rhine by Gustavus struck terror into the Spaniards and Lorrainers, who had thought themselves protected by the river from the vengeance of the Swedes. Rapid flight was now their only security; every place incapable of an effectual defence was immediately abandoned. After a long train of outrages on the defenceless citizens, the troops of Lorraine evacuated Worms, which, before their departure, they treated with wanton cruelty. The Spaniards hastened to shut themselves up in Frankenthal, where they hoped to defy the victorious arms of Gustavus Adolphus. The king lost no time in prosecuting his designs against Mentz, into which the flower of the Spanish troops had thrown themselves. While he advanced on the left bank of the Rhine, the Landgrave of Hesse Cassel moved forward on the other, reducing several strong places on his march. The besieged Spaniards, though hemmed in on both sides, displayed at first a bold determination, and threw, for several days, a shower of bombs into the Swedish camp, which cost the king many of his bravest soldiers. But notwithstanding, the Swedes continually gained ground, and had at last advanced so close to the ditch that they prepared seriously for storming the place. The courage of the besieged now began to droop. They trembled before the furious impetuosity of the Swedish soldiers, of which Marienberg, in Würtzburg, had afforded so fearful an example. The same dreadful fate awaited Mentz, if taken by storm; and the enemy might even be easily tempted to revenge the carnage of Magdeburg on this rich and magnificent residence of a Roman Catholic prince. To save the town, rather than their own lives, the Spanish garrison capitulated on the fourth day, and obtained from the magnanimity of Gustavus a safe conduct to Luxemburg; the greater part of them, however, following the example of many others, enlisted in the service of Sweden. On the 13th of December, 1631, the king made his entry into the conquered town, and fixed his quarters in the palace of the Elector. Eighty pieces of cannon fell into his hands, and the citizens were obliged to redeem their property from pillage by a payment of 80,000 florins. The benefits of this redemption did not extend to the Jews and the clergy, who were obliged to make large and separate contributions for themselves. The library of the Elector was seized by the king as his share, and presented by him to his chancellor, Oxenstiern, who intended it for the Academy of Westerrah, but the vessel in which it was shipped to Sweden foundered at sea.