After expelling the Muslims from Narbonne in 759 and driving their forces back over the Pyrenees, the Carolingian king Pepin the Short conquered Aquitaine in a ruthless eight-year war. Charlemagne followed his father by subduing Aquitaine by creating counties, taking the Church as his ally and appointing counts of Frankish or Burgundian stock, like his loyal William of Gellone, making Toulouse his base for expeditions against Al-Andalus. Charlemagne decided to organize a regional subkingdom the Spanish March, which included part of contemporary Catalonia, in order to keep the Aquitanians in check and to secure the southern border of the Carolingian Empire against Muslim incursions. In 781, his three-year-old son Louis was crowned king of Aquitaine, under the supervision of Charlemagne's trustee William of Gellone, and was nominally in charge of the incipient Spanish March.