The title dux et princeps Francorum, or duke and prince of the Franks, was the title adopted by Pepin of Heristal after his epoch-making victory at the Battle of Tertry in 687. Though previously he had been the mayor of the palace of Austrasia (since 680), by defeating a Neustro-Burgundian army at Tertry he extended his authority over the entire Frankish realm, the first mayor ever to do so. In light of this, he adopted the new titular dignity to indicate his supremacy.
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