The Duchy was held by the family of la Roche until 1308, when it passed to Walter V of Brienne. Walter hired the Catalan Company, a group of mercenaries founded by Roger de Flor, to fight against the Byzantine successor state of Epirus, but when he tried to dismiss and cheat them of their pay in 1311, they slew him and the bulk of the Frankish nobility at the Battle of Halmyros and took over the Duchy. Walter's son Walter VI of Brienne retained only the lordship of Argos and Nauplia, where his claims to the Duchy were still recognized.