The Franks were a Germanic tribe who conquered much of Gaul under their king Clovis in 486. Clovis converted to Christianity, allying the Franks with the Catholic Church and spreading Roman culture throughout Western Europe. Charles Martel defeated the Moors at the Battle of Tours in 732. Pepin III helped the Pope defeat the Lombards, further strengthening the Frankish-Church alliance. Charlemagne greatly expanded the Frankish Empire and was crowned Emperor by the Pope on Christmas Day 800, reviving the Roman Empire. However, the Frankish Empire declined after Charlemagne's death as his grandsons fought over the land and it faced constant invasions.