Charlemagne accepted the summons with alacrity.  With the coming of spring in the following year, 778, and with the full assent of his chief warriors, he began his march toward the Pyrenees, crossed the Loire, and halted at Casseneuil, at the confluence of the Lot and the Garonne, to celebrate there the festival of Easter, and to make preparations for his expedition thence.  As he had but lately done for his campaign in Italy against the Lombards, he divided his forces into two armies:  one composed of Austrasians, Neustrians, Burgundians, and divers German contingents, and commanded by Charlemagne in person, was to enter Spain by the valley of Roncesvalles, in the western Pyrenees, and make for Pampeluna; the other, consisting of Provencals, Septimanians, Lombards, and other populations of the South, under the command of Duke Bernard, who had already distinguished himself in Italy, had orders to penetrate into Spain by the eastern Pyrenees, to receive on the march the submission of Gerona and Barcelona, and not to halt till they were before Saragossa, where the two armies were to form a junction, and which Ibn-al-Arabi had promised to give up to the King of the Franks.  According to this plan, Charlemagne had to traverse the territories of Aquitaine and Vasconia, domains of Duke Lupus II, son of Duke Waifre, so long the foe of Pepin the Short, a Merovingian by descent, and, in all these qualities, little disposed to favor Charlemagne.  However, the march was accomplished without difficulty.  The King of the Franks treated his powerful vassal well; and Duke Lupus swore to him afresh, “or for the first time,” says M. Fauriel, “submission and fidelity; but the event soon proved that it was not without umbrage or without all the feelings of a true son of Waifre that he saw the Franks and the son of Pepin so close to him.”

The aggressive campaign was an easy and a brilliant one.  Charles with his army entered Spain by the valley of Roncesvalles without encountering any obstacle.  On his arrival before Pampeluna the Arab governor surrendered the place to him, and Charlemagne pushed forward vigorously to Saragossa.  But there fortune changed.  The presence of foreigners and Christians on the soil of Spain caused a suspension of interior quarrels among the Arabs, who rose in mass, at all points, to succor Saragossa.  The besieged defended themselves with obstinacy; there was more scarcity of provisions among the besiegers than inside the place; sickness broke out among them; they were incessantly harassed from without; and rumors of a fresh rising among the Saxons reached Charlemagne.  The Arabs demanded negotiation.  To decide the King of the Franks upon an abandonment of the siege, they offered him “an immense quantity of gold,” say the chroniclers, hostages, and promises of homage and fidelity.  Appearances had been saved; Charlemagne could say, and even perhaps believe, that he had pushed his conquests as far as the Ebro; he decided on retreat,