In the tenth century cities began to revive. Those in Lombardy, even in the ninth century, showed signs of returning prosperity. They rebuilt their walls, purchased or manufactured arms, addicted themselves more to commercial industry, and acquired some wealth; and, as a natural consequence of this, they felt the desirableness of self-government and self-defence. About the same time, the political institutions of the towns of Lombardy underwent a change. The bishops, in many instances, became counts or temporal governors of their sees. The citizens elected their own magistrates, subject to the approval of the bishops; the emperor--though not always without the consent of the people--appointing them to their sees, in consequence of the introduction of the feudal principle into the church, the prelates having become temporal lords and feudatories of the empire. The emperors also appointed commissioners or vicars for these towns, who there represented the imperial authority. The episcopal government in cities seems to have been favourable to the growing independence of the towns, the churchman, even if disposed, being by no means able to become so formidable an oppressor as the soldier, while the consent, at least, of the people, on his appointment, kept up a notion of their municipal importance. During, and after the war of investitures, when the cities of Italy took part in the quarrel between the emperor and the pope, some arraying themselves on one side and some on another, they received an impulse which quickened their desire for independence.