The Lombard league took its final shape in the beginning of 1168, when Frederick was refreshing his exhausted forces at Pavia. The members pledged themselves to aid each other against all those who would make war against them, or would exact anything more from them than had been customary. They also appointed rectors, chosen from among the consuls of the several cities, for the management of federal affairs. Fear of the Emperor had now destroyed even the jealousies of neighbouring and rival cities, and the league now included all the towns of the northern plain, from Milan to Venice, and from Bergamo to Bologna. Lodi itself now made common cause with its old enemy Milan, and even the obstinate imperialists of Pavia grudged to the beaten Emperor the protection of its walls. All the approaches to the northern Alpine passes were blocked by the confederate cities, and the Emperor could only get home by a long detour through the uplands of Montferrat and Piedmont. In the spring of 1168 Frederick made his way to Susa, and thence over the Mont Cenis. After his departure, new accessions increased the Lombard league, and Alexander III. sent it his blessing. [Sidenote: Foundation of Alessandria, 1168.] In the spring of 1168 the league founded a new city in a marshy district, on the banks of the Tanaro, and called it Alessandria in honour of its patron. Vast earthworks and a strong castle made their creation an impregnable fortress, calculated to hold out as long as provisions remained. The town soon prospered: the Pope erected it into a bishopric, and settlers from all sides made it a busy centre of trade. The foundation of Alessandria pushed the league’s territory more to the westwards, into the region where the feudal potentates were still strong, and where cities like Asti, Vercelli, Novara, were now emboldened to join it. Moreover, the city protected the high road from Milan to Genoa which gave Lombardy access to the sea, and blocked the descent of German armies from the Burgundian passes as effectively as the league had already blocked the northern valleys of the Alps. [Sidenote: The Antipope Calixtus III.]