By the early 8th century the monastic orders had built the faith in western Europe into a bulwark against Muslim iconoclastic fervour, from which a new force was able to turn the tide of invasion. In 714 Charles Martel, Pepin of Herstal's illegitimate son,had seized the initiative,soundly defeating the Neustrians again,asserting his authority over northern Gaul and restoring Frankish dominion in the south. He then turned to confront the advancing Muslims and repulsed them at Poitiers in 732. Charles reclaimed the south-west and went on to frustrate Muslim designs on Provence. He then reasserted Frankish authority over the Germans east to Thuringia and south in Bavaria.