Frederick used this opportunity to revive the old Roman laws, or at least, to have a code of laws drawn up, which should define his rights and those of the reigning princes under him. Four doctors of the University of Bologna were selected, who discovered so many ancient imperial rights which had fallen into disuse that the Emperor's treasury was enriched to the amount of 30,000 pounds of silver annually, by their enforcement. When this system came to be practically applied, Milan and other Lombard cities which claimed the right to elect their own magistrates, and would have lost it under the new order of things, determined to resist. A war ensued: the little city of Crema was first besieged, and, after a gallant defence of seven months, taken and razed to the ground. [Sidenote: 1162.] Now came the turn of Milan. In the meantime the Pope, Adrian IV., had died, after threatening the Emperor with excommunication. The college of cardinals was divided, each party electing its own Pope. Of these, Victor IV. was recognized by Frederick, who claimed the right to decide between them, while most of the Italian cities, with France and England, were in favor of Alexander III. The latter immediately excommunicated the Emperor, who, without paying any regard to the act, prepared to take his revenge on Milan. In March, 1162, after a long siege, he forced the city to surrender: the magistrates appeared before him in sackcloth, barefoot, with ashes upon their heads and ropes around their necks, and begged him, with tears, to be merciful; but there was no mercy in his heart. He gave the inhabitants eight days to leave the city, then levelled it completely to the earth, and sowed salt upon the ruins as a token that it should never be rebuilt. The rival cities of Pavia, Lodi and Como rejoiced over this barbarity, and all the towns of northern Italy hastened to submit to all the Emperor's claims, even that they should be governed by magistrates of his appointment. In spite of this apparent submission, he had no sooner returned to Germany than the cities of Lombardy began to form a union against him. They were instigated, and secretly assisted, by Venice, which was already growing powerful through her independence. The Pope whom Frederick had supported, was also dead, and he determined to set up a new one instead of recognizing Alexander III. He went to Italy with a small escort, in 1163, but was compelled to go back without accomplishing anything but a second destruction of Tortona, which had been rebuilt. In Germany new disturbances had broken out, but his personal influence was so great that he subdued them temporarily: he also prevailed upon the German bishops to recognize Paschalis III., the Pope whom he had appointed. He then set about raising a new army, and finally, in 1166, made his _fourth_ journey to Italy. [Sidenote: 1166. FOURTH JOURNEY TO ITALY.]