The battle of Poitiers was a referendum of looters versus soldiers

From Carnage and Culture by Victor Davis Hanson. Page 143.

For much of the seventh century the Muslims, with relatively small mounted forces, had swept aside a variety of weak enemies—the Sassanid Persians and overextended Byzantines in Asia, and Visigoths in North Africa and Spain. When Abd ar-Rahman crossed the Pyrenees, however, he encountered an entirely new force in the Franks. French scholars of the battle were largely correct when they pointed out that the Arabs had been successful against similarly nomadic interlopers like the Visigoths and Vandals, who had themselves migrated into North Africa and Spain, but hit a wall against the Frankish rustics who were indigenous to Europe. In their eyes, the battle of Poitiers was a referendum of looters versus soldiers “sédentarisés,” who stayed in one place, owned property, and considered battle more than a raid.

The Franks, descendants of the Germani described by Tacitus in the first century A.D., originally lived in what is now Holland and in eastern Germany around the lower Rhine. They seemed to have migrated in large numbers into nearby Gaul by the fifth century. Scholars do not agree on the origin of the word “Franks”; most associate it with either their famed throwing ax, the francisca, or the old Germanic word freh/frec, meaning “brave” or “wild.” In any case, under Clovis (A.D. 481–511) the Frankish tribes united in the old Roman province of Gaul in what came to be known as the Merovingian monarchy, named after the legendary Frankish chieftain Merovech (Merovaeus), grandfather of Clovis, who had fought against the Huns at Châlons (A.D. 451).

After Clovis’s death a series of dynastic wars among his offspring led to independent kingdoms: Burgundy to the southeast in the valleys of the upper Seine, Rhône, and Loire Rivers; Austrasia to the east across the Meuse, Moselle, and Rhine Rivers; and Neustria in the west along the large plains bordering the Atlantic coast. By 700 Gaul was a petty kingdom of warring states until the reign of Charles Martel; nevertheless, the Franks increasingly saw themselves more as a nation than a tribe, more in the classical than in the Germanic tradition. Indeed, the Merovingians sought to trace their Frankish ancestry not back to the dark forests of Germany, but to migrations of mythical Trojans after the conquest of Troy.

Charles Martel was not in direct line of succession to the Merovingian throne, but the bastard son of King Pippin. Despite the absence of a legal claim on the Frankish kingdom—Charles was mayor of the palace, equivalent to being a duke of the Austrasian Franks—he engaged in a lifelong effort to unite these kingdoms. His eventual victories provided the foundation of the much larger, stronger Carolingian dynasty, which under his grandson Charlemagne saw the reunification of central Europe. In eighteen years of uninterrupted civil war, from 714 to 732, Charles consolidated the old tripartite realm of Clovis and then quickly expanded his rule throughout Gaul. Almost every year of the reign of Charles until his death in 741 was spent in warring to unite Gaul or to rid Europe of Islam. In 734 he fought in Burgundy; the next year he furthered his consolidation of Aquitaine. The years 736–41 saw war once more in Burgundy, in Provence, and against the Saxons. This yearly fighting eventually allowed his son Pippin (751–680) to rule over a united Francia officially as the first Carolingian king. It is often forgotten in accounts of Poitiers that when Charles brought his infantrymen to the battlefield, they were hardened veterans from nearly twenty years of constant combat against a variety of Frankish, German, and Islamic enemies.