The Battle of Tours is one of these events that while having a real importance by themselves, outgrow their immediate and consequential results and take a life on their own.
GAUL IN THE EARLY VIIIth CENTURY
It is first necessary to see what happened in Gaul at the turn of the VIIIth century, specifically in 718.Arnulfids, also known as Peppinids and later Carolingians, had managed to roughly unify the three Frankish realms (Neustria, Austrasia, Burgundy) under their rule,Peppin II of Herstal being the sole majordomos (mayor of the palace), as Merovingian authority significantly declined due to several minority crises : whole peripherial regions which formerly acknowledged Merovingian authority (Aquitaine, Provence, Alemania, Thuringia, Bavaria) or at least some remote tributary relations (Saxony, Kent) simply went out of the Frankish sphere of influence and became largely independent.Charles Martel had to fight for imposing himself as the successor of Peppin II during four years against his half-brothers supported by Ugobertides, while Ethiconides rather supported Charles. All of these being powerful families of Austrasia, the eastern Frankish realm which took more political and economical importance in the VIIth, partly due to the shift of trade roads.After having defated his brother, Charles immediatly fought with Ragnared, the new majordomo of Neustria, supported by the new king Chilperic II : it's really hard to be assertive there, but it might have quite possibly been a Merovingian reaction against Arnulfid takeover of Francia, supported by an aristocracy still loyal to the dynasty from one hand, and which had to loose regional power if Charles won. As such, Ragnafred and Chilperic II fruitlessly first allied themselves to Frisians, a pagan people which dominated North Sea trade, and when it failed, with Eudon of Aquitaine.
The duke Eudon ruled over Aquitaine, a region without palace (and then no place of political redistribution for the local aristocracy) but more or less considered as an outer sub-realm of Francia. Furthermore, he also ruled over Vascons, famed for their light horsemen, of both Wasconia (which gave Gascony) and Vasconia (roughly the pyrenean region, altough it's not really clear how much south of Pyrenees is authority ended).Aquitaine was wealthy, and culturally apart from the rest of Frankish world : each realm tended to be, bearing a specific political identity, but Aquitaine had a more Mediterranean outlook, still considering themselves as Romans (the difference with Franks being rather not a difference of degree of romanisation, but how this romanisation looked lile) and considered as quasi-foreigners by Franks (and outright foreigners and raiders when it came to Vascons).By allying with Ragnafred and Chilperic, Eudon saw his power acknowledged by the Neustrian court, Eudon is considered as the dominus-princeps of Aquitaine, some equivalent to a majordomo and sub-king (barcers serving as regalia, for exemple).While Ragnafred was defeated and the power of Charles enforced, Eudon still remained largely undisputed in Aquitaine, and Charles had to accept it for the moment.
It's at this point that Arabo-Berbers, already having conquered Gothic Spain and a short pause, resumed their raids and conquests : it's not clear when exactly this did happened but it's probable that in 719, during the time al-Sahm ibn Malik was wali of al-Andalus, the last Gothic holdout of Narbonne was taken.Now, this probably wasn't a surprise for Franks and Aquitains, the conquest of Spain having happened in the first part of the decade, but it's possibly they didn't know what to make of it : it's telling that no Gaulish chronicle records the conquest of Africa or in general Arabo-Islamic conquests so far.
BATTLE OF TOULOUSE - 721
Nevertheless, al-Sahm, after having secured control of Gothia (meaning the part of Gaul that belonged to Goths, which roughly is the Lower Languedoc) targeted the city of Toulouse and besieged it in 721. According the Mozarabian Chronicle (written in 754, a main and necessary source on the events), he went there with siege engines, intending to take and hold the city as he did with Narbonne.Eudon, with an army of Aquitains, Vascons and Franks, went and fought the Arabo-Berbers (possibly reinforced by Gothic cavalrymen) outside Toulouse (it's not really know where, but almost certainly along the Roman Road), managing to attack their rear, and pushing them back after having killed al-Sahm.
This Battle of Toulouse of 721 represented the first serious defeat of Arabo-Bebers in the west since they entered Spain, and while it did not stop raids to happen, Aquitaine was spared them for a while.Eudon was at the peak of his prestige, being a quasi-king which scored a main victory against an apparently unstoppable people, and according the Liber Ponctificalis' account of the event, was considered as the defender of Christiendom as the Papacy sent blessing and eucharistic sponges before the battle, as the Arabo-Berbers movement against Aquitaine would have been on the cards.
After the battle, Arabo-Berbers still controlled the former Gothic province of Gaul, but had only a garrison at Narbonne (Arbûna), the rest of the land being (like a significant chunk of Muslim Spain) let to Christian nobility and clergy to rule for them.