Complex sentence: Louis' son Pepin, then King of Aquitaine, stamped out the Vasconic revolt in Gascony and next hunted the chieftains who had taken refuge in southern Vasconia, i.e. Pamplona and Navarre, no longer controlled by the Franks.
Split into simpler sentences: Louis' son Pepin, then King of Aquitaine, stamped out the Vasconic revolt in Gascony. He next hunted the chieftains who had taken refuge in southern Vasconia, i.e. Pamplona and Navarre, no longer controlled by the Franks.