The Saxons were the only remaining German people who resisted both the Frank rule and the introduction of Christianity. They held all of what is now Westphalia, Hannover and Brunswick, to the river Elbe, and were still strong, in spite of their constant and wasting wars. During his first campaign, in 772, Charlemagne had overrun Westphalia, taken possession of the fortified camp of the Saxons, and destroyed the "Irmin-pillar," which seems to have been a monument erected to commemorate the defeat of Varus by Hermann. The people submitted, and promised allegiance; but the following year, aroused by the appeals of their duke or chieftain, Wittekind, they rebelled in a body. The Frisians joined them, the priests and missionaries were slaughtered or expelled, and all the former Saxon territory, nearly to the Rhine, was retaken by Wittekind. Charlemagne collected a large army and renewed the war in 775. He pressed forward as far as the river Weser, when, carelessly dividing his forces, one half of them were cut to pieces, and he was obliged to retreat. His second expedition to Italy, at this time, was made with all possible haste, and a new army was ready on his return. Westphalia was now wasted with fire and sword, and the people generally submitted, although they were compelled to be baptized as Christians. In May, 777, Charlemagne held an assembly of the people at Paderborn: nearly all the Saxon nobles attended, and swore fealty to him, while many of them submitted to the rite of baptism. [Sidenote: 777. ASSEMBLY AT PADERBORN.] At this assembly suddenly appeared a deputation of Saracen princes from Spain, who sought Charlemagne's help against the tyranny of the Caliph of Cordova. He was induced by religious or ambitious motives to consent, neglecting for the time the great work he had undertaken in his own Empire. In the summer of 778 he crossed the Pyrenees, took the cities of Pampeluna and Saragossa, and delivered all Spain north of the Ebro river from the hands of the Saracen Caliph. This territory was attached to the Empire as the Spanish Mark, or province: it was inhabited both by Saracens and Franks, who dwelt side by side and became more or less united in language, habits and manners. On his return to France, Charlemagne was attacked by a large force of the native Basques, in the pass of Roncesvalles, in the Pyrenees. His warriors, taken by surprise in the narrow ravine and crushed by rocks rolled down upon them from above, could make little resistance, and the rear column, with all the plunder gathered in Spain, fell into the enemy's hands. Here was slain the famous paladin, Roland, the Count of Brittany, who became the theme of poets down to the time of Ariosto. Charlemagne was so infuriated by his defeat that he hanged the Duke of Aquitaine, on the charge of treachery, because his territory included a part of the lands of the Basques.