In June, 1135, the Imperial envoy Engelbert entered Florence, and seemed amicable to the Commune.[148] He speedily moved on to Lucca, where he met with a serious defeat. The succeeding envoy, Errico of Bavaria, came with a considerable force, and appeared ill-disposed towards the Florentines. His stay, however, was short, and his successor, Ulrico d'Attems, showed friendly intentions, and in 1141 even aided the Florentines in a skirmishing expedition against Sienna.[149] But all these envoys came and disappeared like meteors. Florence was now beginning its great war with Count Guido, surnamed the Old, who had become their foe. A contested inheritance served as a pretext for the rupture; but the real cause must have lain in the increased power and menacing attitude of the count. His possessions hemmed in the Republic on all sides, and Sanzanome said of him, "Per se quasi civitas est et provincia."[150] The citizens first seized a castle of his near Ponte a Sieve, and then attacked his stronghold of Monte di Croce. But, aided by neighbouring towns, the count succeeded in defeating the Florentines on June 24, 1146. Nevertheless, they contrived even then to extort advantageous terms, namely: that part of the walls should be dismantled, and that the castle should hoist the banner of Florence.[151] All this was done, and there was truce for a time, while the count seems to have been engaged on distant expeditions. But later, the walls were restored, and thereupon the Florentines,[152] declaring that the agreement had been violated, suddenly stormed the castle in 1153, and rased it to the ground. And thus, wrote Sanzanome, "_Mons Crucis est cruciatus_." Certainly all this could not lead to peace. Count Guido ceded part of Poggibonsi to the Siennese on condition of their fortifying and defending it against the Florentines, who were preparing to make an assault. By accepting the gift Sienna stood pledged to play an active part in the war, which thus continued to spread.[153] II.