In 730, the Land of the Franks appeared to be wide open for conquest. The Franks were the most primitive people the Muslims had yet fought, and their Merovingian kings had become increasingly powerless. The border areas were especially decentralized; until the late Middle Ages, Toulouse was independent and often allied against Paris. Even the Duke of Aquitaine who had driven the Muslims from Toulouse chose alliance with them against the Franks. France should have been a reprise of the Spanish conquest.
However, after 50 years, the Muslim invasion was no longer a surprise attack. Frankia was a real homeland with loyal Frankish farmers, not a place like Iberia where the aristocrats were hated. For the Franks, imagine people like Vikings; they were named for a kind of axe. And although the King in Paris was powerless, just like in Tolkien’s Gondor, the Steward was growing stronger. Charles began drilling an army as soon as Muslim invaders settled in Marseille.
In 732, a local Muslim rebellion brought the main force of the Arab fighting men into the north. They killed the rebel emir and attacked his ally Aquitaine, devastating the heartland of Celtic Gaul. The defeated Duke of Aquitaine now sent word to the Franks, agreeing to their overlordship in return for help.
For the first time, the Muslim invaders met a defensive army that was large, well-trained, and not caught by surprise. In fact, the Muslim army was surprised to find defenders at all. Heading north to sack the city of Tours before heading back to Spain for the winter, they found a Frankish shield wall across the top of a wooded hill near Poitiers.
For a week, the Muslim raiding parties gathered their main force until they felt strong enough to attack, but Charles Martel had chosen his position carefully. The Muslim cavalry had to charge uphill and through trees, which diminished the shock of their attack. They were not able to break the shield wall. They had never met the ferocity of Frankish feudalism, either. In these battles, if either side could kill the general or king, it meant victory. Charles’s men stood thickly around him, heavily armed, and kept him safe.
Frankish victory came when some Franks ran down to the Arab camp in the valley and began freeing their captives. When a party of cavalry rode back to deal with this threat, the rest of the Muslims thought a retreat had been called. In the confusion, their general was killed. As night fell, the Muslim raiders abandoned their camp and fled.
Muslim armies never came that far north again (until they besieged Vienna from another direction). Charles Martel, his son Pippin and grandson Charlemagne built up Frankish military power so that the Muslims were trapped into a Cold War. There were flashpoints around Toulouse and Narbonne, but the Franks were always on hand to aid allies. Modern France began as a military alliance against Muslim invasion. By the time Charlemagne’s descendants had begun infighting and splitting up the alliance, the Visigothic nobles had launched their Reconquista.