Since the establishment of the Frankish kingdom by Clovis in 509, the Franks have been at constant odds with the Saxons. The Liber Historiae Francorum recounts an early expedition in 555 to punish them and another passage notes fifteen years later, Chilperic joins his brother with an army to fight the Saxons. The Historian also recounts the battle between the Saxon Bertoald and Dagobert I of Austrasia, ending in a Frankish victory with the timely arrival of reinforcements.
The Chronicle of Fredegar, writing a history of the Franks, records in 613 of Saxon assistance to King Theudebert of Austrasia in his conflict with the Neustrian King Theuderic. However, Theuderic won the war and in a later passage, Fredegar notes, Saxon promises are not worth much.
J.M. Wallace-Hadrill, a historian of the Merovingian age, describes the back-and-forth skirmishes between Franks and Saxons were actually attempts to gain a foothold in Frankish tribal lands up to the time of Charles Martel. Saxon expansion took place during a time of upheaval, while Charles Martel was engaged in a conflict with the old regime. Following his victory at Soissons in 719, Charles marched east to punish the Saxons.
The Saxons did not remain quiet as they rebelled again in 724 and 738, both instances were suppressed by punitive expeditions. Led by Charles in person, he thoroughly laid waste to the region taking hostages. Fouracre notes in his biography of Charles Martel, his campaigns were meant to limit further Saxon expansion rather than conquer Saxony itself, that step would be accomplished by his grandson.
To explain the nature behind the ‘back-and-forth’ contact, Timothy Reuter in Germany in the Early Middle Ages 800 – 1056, describes the political structure of the Saxons in the pre-Carolingian period. At its base was the Gau with a single ruler and the 100 Gau, varying in size and number, formed three provinces; Westfalia, Engraving and Ostfalia. Legislation was made collectively through an annually held assembly, represented by all the Gau-rulers, twelve from each caste; the nobiles, the frilingi, and the lazzi. Through the assembly, legislation could make political decisions negating the need for a monarchical power and decide on military leadership if needed, surprisingly, each Gau was independent to make war or peace.
The division of the people into castes played a significant role, as the nobiles readily accepted Christianity, some even built churches and monasteries, the lower classes seemingly resisted Frankish rule and retained their pagan beliefs.
Chronicle of Fredegar, begins with the creation of the world and ends in 642 AD.
The Continuations, rework of the Chronicle of Fredegar, new sections bring events to 768 AD.
Hadrill, The Long-Haired Kings.
Fouracre, Charles Martel.
Reuter, Germany in the early Middle Ages 800 – 1056.