Battle of Tertry

In 687, the Battle of Tertry pitted the Austrasian army led by Pepin of Herstal, mayor of the palace, against the Neustrian forces led by Berchaire and the Merovingian king Theuderic III. This resounding victory for Pepin confirms the supremacy of the Austrasian palace mayors, relegating the Merovingian kings to a purely symbolic role. Berchaire is captured, and Theuderic III must recognize the authority of Pepin, who becomes the true master of the Frankish kingdom.

Since the death of Dagobert I, the Frankish kingdom has been divided between Neustria and Austrasia, officially governed by the Merovingian kings but increasingly dominated by their palace mayors. The rivalries between these entities lead to a series of conflicts, of which Tertry constitutes the apogee. Pepin of Herstal, at the head of the Austrasian troops, sought to impose his authority over the entire Frankish kingdom. Neustria, weakened by internal divisions and a less solid command, found itself on the defensive.

The sources provide few precise details. Pepin would have taken advantage of the disorganization of the Neustrian forces to lead a decisive attack. The element of surprise, encirclement and the superior discipline of the Austrasian army seem to have played a major role. The geography of Tertry, located between the Somme and the Oise, may have favored the maneuver of Pepin's troops and the capture of Berchaire.

Tertry's victory opens a new political era: the Merovingian kings, now described as 'lazy kings', retain their title but are deprived of any effective power. Pepin of Herstal inaugurates the Pippinides dynasty, which will give birth to the Carolingians with his descendant Charlemagne. The centralization of power around the mayor of the palace marks the foreshadowing of the Carolingian monarchy and the unified kingdom of France.