Leyva, well acquainted with the difficulties under which his countrymen labored, and the impossibility of their facing, in the field, such a powerful army as formed the siege of Pavia, placed his only hopes of safety in his own vigilance and valor. The efforts of both were extraordinary, and in proportion to the importance of the place with the defence of which he was intrusted. He interrupted the approaches of the French by frequent and furious sallies. Behind the breaches made by their artillery he erected new works, which appeared to be scarcely inferior in strength to the original fortifications. He repulsed the besiegers in all their assaults, and by his own example brought not only the garrison, but the inhabitants, to bear the most severe fatigues, and to encounter the greatest dangers, without murmuring. The rigor of the season conspired with his endeavors in retarding the progress of the French. Francis, attempting to become master of the town by diverting the course of the Tessino, which is its chief defence on one side, a sudden inundation of the river destroyed, in one day, the labor of many weeks, and swept away all the mounds which his army had raised with infinite toil as well as at great expense. Notwithstanding the slow progress of the besiegers, and the glory which Leyva acquired by his gallant defence, it was not doubted but that the town would at last be obliged to surrender. Pope Clement, who already considered the French arms as superior in Italy, became impatient to disengage himself from his connections with the Emperor, of whose designs he was extremely jealous, and to enter into terms of friendship with Francis. As Clement's timid and cautious temper rendered him incapable of following the bold plan which Leo had formed of delivering Italy from the yoke of both the rivals, he returned to the more obvious and practicable scheme of employing the power of the one to balance and to restrain that of the other. For this reason he did not dissemble his satisfaction at seeing the French King recover Milan, as he hoped that the dread of such a neighbor would be some check upon the Emperor's ambition, which no power in Italy was now able to control. He labored hard to bring about a peace that would secure Francis in the possession of his new conquests; and as Charles, who was always inflexible in the prosecution of his schemes, rejected the proposition with disdain, and with bitter exclamations against the Pope, by whose persuasions, while Cardinal di Medici, he had been induced to invade the Milanese, Clement immediately concluded a treaty of neutrality with the King of France, in which the republic of Florence was included.