Chef d'escadron
In the French armed forces, Chef d'escadron is the title of a commandant in the Cavalry, Artillery and Baggage Train Corps and in the Gendarmerie.
In the Armoured Cavalry Corps, the equivalent rank is Chef d'escadrons, in the Infantry and the Combat Engineer Corps, it is Chef de bataillon.
Confusingly, escadrons in the actual French army's Armour and Baggage Train Corps are company equivalents and therefore typically commanded by a capitaine.