The Lombards entered Italy in 568 and soon established themselves in the valley of the Po. For some years the boundary line between them and the Byzantine possessions, that is, the lands still held by the emperor, ran, roughly speaking, from Monselice (near Padua) west to Mantua, then southwest to Reggio, then northwest to Parma, then southwest to Berceto in the Apennines. But after Authari (583-90) became king of the Lombards he renewed the war of conquest which had been interrupted for a few years. He and his successors conquered the Byzantine possessions bit by bit and added them to the Lombard kingdom. In this way Lombardy was slowly enlarged and the Byzantine land, which was called the "province Italy" (Italia provincia), was correspondingly reduced in size. Success made the Lombard kings more ambitious and led them to plan the conquest of all Italy. A great step forward was taken in 749 when Aistulf took Ravenna, drove out the exarch, and put an end to the Byzantine rule in central Italy. Tuscany, which was separated from Liguria by a line from Luna to Berceto, was already in their hands, and Corsica, after suffering several invasions, had finally been occupied by them in the eighth century. Venice, Istria, and the duchies of Rome, Spoleto, and Benevento were next attacked, but they united to resist their common enemy, and put themselves under the protection of the pope. Under these circumstances Stephen II (752-757) saw an opportunity to unite all these provinces and to make himself their political head. He determined to try to succeed to the power of the emperor in Italy. He accordingly went to France and secured the promise from Pippin to give him all the above-named territories and to force the Lombards to withdraw from them into the territory which they had first occupied. See no. 6. It was an ambitious plan which Stephen II formed, but he could not carry it into effect. Pippin fulfilled his promise only in part, and the pope was content with a few cities and the promise of Aistulf that he would never again attack any of the territories named in Pippin's promise. Desiderius (756-774), however, did not keep the promise which Aistulf, his predecessor, had given, but made war on the duchy of Rome. Adrian I (772-795) called on Karl the Great to come to his aid. Karl came, and, while spending Easter (774) at Rome, at the earnest request of Adrian, renewed the promise of his father. But Karl did not keep this promise which had been so solemnly made. Contrary to the wishes of the pope he made himself king of the Lombards and thereby inherited the ambitions, pretensions, policy, and interests of the Lombard kings. The situation was changed. To Karl, as well as to the dukes of Benevento and Spoleto, and to the people of Istria, an increase in the power of the pope was no longer a desirable thing. So Karl refused to keep his promise. Adrian angrily protested. But Karl was deaf to protests and threats. Their