In fact it was solely due to the intelligence and leadership of Charles Martel (c. 686 -- 22 October 741) -- a Frankish statesman and military leader who, as Duke and Prince of the Franks and Mayor of the Palace, was de facto ruler of France from 718 until his death -- that Europe was not conquered and converted to Islam.
After unifying Gaul, Charles dealt with the Islamic advance into Western Europe by Arab and Berber Islamic forces which had already conquered Spain. The caliphate forces crossed the Pyrenees (720), defeated the Visigoths (721-725) under Abdul Rahman Al Ghafiqi, Governor-General of al-Andalus, advanced on Tours, "the holy town of Gaul".
In October 732, the army of the Umayyad Caliphate led by Al Ghafiqi met Frankish and Burgundian forces under Charles in an area between the cities of Tours and Poitiers. That marked an important Frankish victory known as the Battle of Tours or ma'arakat Bal ash-Shuhad , Battle of the Palace of Martyrs. Charles, after Tours destroyed Arabs' fortresses at Agde, Beziers and Maguelonne, and defeated them again in Nimes, though ultimately failing to recover Narbonne (737). By 721, the emir of Córdoba had built up a strong army from Morocco, Yemen, and Syria to occupy Aquitaine. The invading Muslims besieged Toulouse, then Aquitaine's main city.
Charles then concentrated his attention to the Umayyads, virtually for the remainder of his life. Due to the situation in Iberia, Charles thought he needed a standing army made of professional soldiers, a concept unknown since Roman times as a core of veterans who would be augmented with the usual conscripts called up in time of war. He needed a core army to challenge the feared Muslim heavy cavalry, and he needed to pay them well so that their families could buy the food they would have otherwise grown. To get the money he had no choice but to seize church lands and property, which he did.
It was under one of the ablest and most renowned Muslim generals, with an army of veterans, and the advantage of time, place, and circumstance, that the Arabs made their great effort at the conquest of Europe, north of the Pyrenees. Odo, the hero of Toulouse, was badly defeated in the Muslim invasion of 732 at the battle prior to the Muslim sacking of Bordeaux, and again at the Battle of the River Garonne after he had gathered a second army. Odo then fled to Charles, seeking help. Charles agreed to come to Odo's rescue, provided Odo acknowledged Charles and his house as his overlords, which Odo did formally at once. Odo and his remaining Aquitanian formed the right flank of Charles's forces at Tours. Charles then defeated the Moors commanded by Abderame.
Muslims forces had not yet given up their plans and in 736 a new invasion by sea was launched by Abdul Rahman's son. It landed in Narbonne and moved at once to reinforce Arles and move inland. Charles descended on the Provençal strongholds of the Umayyads and in 736 he retook Montfrin and Avignon, and Arles and Aix-en-Provence with the help of Liutprand, King of the Lombards. Nîmes, Agde, and Beziers, held by Islam since 725, fell to and their fortresses were duly destroyed.
Then Charles Martel crushed one Umayyad army at Arles and then took the city itself by a direct and brutal frontal attack, then burned it to the ground to prevent its use again as a stronghold for Umayyad expansion. He then moved swiftly and defeated a mighty host at the River Berre.
Several historians, including Sir Edward Creasy, believe that had he failed at Poitiers, Islam would probably have overrun Gaul, and perhaps the remainder of Western Europe. Gibbon made clear his belief that the Umayyad armies would have conquered from Japan to the Rhine, and even England, having the English Channel for protection, with ease, had Charles not prevailed.
Creasy said "the great victory won by Charles Martel " gave a decisive check to the career of Arab conquest in Western Europe, rescued Christendom from Islam, [and] preserved the relics of ancient and the germs of modern civilization."