Derby moved rapidly and took the French army by surprise, defeating them in a running battle. French casualties were heavy, with many killed and a large number captured, including their commander. The surviving French from their field army rallied around John, Count of Armagnac, and retreated north to Périgueux. Within days of the battle, Bergerac fell to an Anglo-Gascon assault and was subsequently sacked. After consolidating and reorganising for two weeks Derby left a large garrison in the town and moved north to the Anglo-Gascon stronghold of Mussidan in the Isle valley with 6,000–8,000 men. He then pushed west to Périgueux, the provincial capital, taking several strongpoints on the way.