Desiderius, enraged to the extreme both against Charlemagne and the Pope, held the latter principally responsible for the affront put upon his daughter, and resolved to wreak vengeance at once. He demanded that the Pope should crown the son of Carloman as King of the Franks, intending after that to incite an uprising in that country in his favor. The time seemed auspicious, as Charlemagne was now at war with the Saxons. While the Pope was hesitating, and just as Desiderius was about to use force, Stephen died and was succeeded by Hadrian.
Hadrian could not be induced to crown the young prince, either by flattery or by threats. Desiderius thereupon began harrying the Papal territory and advanced to lay siege to Rome. As he occupied all land communications, Hadrian sent messengers to Marseilles and thence to Diedenbofen[21] the seat of Charlemagne’s court at that time. In his letter Hadrian informed the King of Desiderius’s demand and his threatening movement, and implored him not to let him fall into Desiderius’s hands. Immediately after the receipt of this letter Charlemagne received one from Desiderius, in which the latter, to gain time for carrying out his designs against Rome, assured him he had given up everything to the Pope which belonged to him.
Charlemagne, however, was not deceived. The favor which Desiderius had shown to the son of Carloman clearly revealed his hostility to himself. He decided upon war with the Lombards at once, and the campaign was begun in the autumn of the year 773.
Charlemagne mustered his forces at Geneva. Their equipment was essentially different from that formerly used by the Franks. They were armed with the longer Roman spear as well as the larger shield, the latter furnishing better protection for the body than the round Frankish shield. In place of the old leathern head-covering they wore the brazen helmet and visor. The body was also protected by a coat of mail. Many of the soldiers carried heavy clubs in place of the long swords. These formidable weapons were made of knotted oak, cased in iron, and sometimes made entirely of that metal.
Upon the advice of those Franks who were hostile to Charlemagne and had been entertained at the court of Desiderius, the Alpine passes leading into Lombardy were obstructed besides being strongly guarded. In this way Desiderius felt certain he could defy Charlemagne. Another event increased his feeling of security. Charlemagne, in consideration of the natural resentment of a father whose daughter had been humiliated, sought once more to establish friendly relations with him. He appealed to him to acquiesce in Pepin’s assignment of territory to the Church and to abstain from any assault upon his sovereignty. Unfortunately for Desiderius, he looked upon this as a proof that Charlemagne recognized the impossibility of invading Italy. Thereupon he contemptuously rejected the offer and went so far with his insolence that the latter, realizing now that war was inevitable, exclaimed: “He does not fear the barking of the German dog so long as it does not come out of its kennel.”