The exigencies of war in his vast empire now called Charlemagne to Spain, where the Arabs had become troublesome and needed chastisement.  Not far had he marched away when Wittekind was again in Saxony, passing from tribe to tribe through the forests of the land, and with fiery eloquence calling upon his countrymen to rise against the invaders and regain the freedom of which they had been deprived.  Heedless of their conversion, disregarding their oaths of allegiance, filled with the free spirit which had so long inspired them, the chiefs and people listened with approval to his burning words, seized their arms, and flew again to war.  The priests were expelled from the country, the churches they had built demolished, the castles erected by the Frank monarch taken and destroyed, and the country was laid waste up to the walls of Cologne, its Christian inhabitants being exterminated.

But unyielding as Wittekind was, his great antagonist was equally resolute and persistent.  When he had finished his work with the Arabs, he returned to Saxony with his whole army, fought a battle in 779 in the dry bed of the Eder, and in 780 defeated Wittekind and his followers in two great battles, completely disorganizing and discouraging the Saxon bands, and again bringing the whole country under his control.  This accomplished, he stationed himself in their country, built numerous fortresses upon the Elbe, and spent the summer of 780 in missionary work, gaining a multitude of converts among the seemingly subdued barbarians.  The better to make them content with his rule he treated them with great kindness and affability, and sent among them missionaries of their own race, being the hostages whom he had taken in previous years, and who had been educated in monasteries.  All went well, the Saxons were to all appearance in a state of peaceful satisfaction, and Charles felicitated himself that he had finally added Saxony to his empire.

He deceived himself sadly.  He did not know the spirit of the free-born Saxons, or the unyielding perseverance of their patriotic leader.  In the silent depths of their forests, and in the name of their ancient gods, they vowed destruction to the invading Franks, and branded as traitors all those who professed Christianity except as a stratagem to deceive their powerful enemy.  Entertaining no suspicion of the true state of affairs, Charlemagne at length left the country, which he fancied to be fully pacified and its people content.  With complete confidence in his new subjects, he commissioned his generals, Geil and Adalgis, to march upon the Slavonians beyond the Elbe, who were threatening France with a new barbarian invasion.