1246 Death of Geoffrey. His brother Guillaume Villehardouin succeeds. He proposes to complete conquest of Peloponnesus.
1247 Conquest of Nauplia with help of Venetians of Modon.
1248 Conquest of Monemvasia. Before the end of the year the entire Peloponnesus is under Frankish domination.
1259 Guillaume assists his father-in-law Michael II of Epirus in his war against Michael VIII of Constantinople. Battle of Pelagonia, and capture of Guillaume, by Michael VIII.
1261 Guillaume released by ceding Monemvasia, Misithra, and Maina, three strong cities, to Michael VIII.
Pope Urban IV releases Guillaume from promise not to wage war on Michael. Warfare results in the Morea.
1263 Urban IV mediates between Michael and Guillaume.
1267 The principality becomes a dependency of the kingdom of Naples, having been that of the Romanian emperors.
1277 Death of Guillaume. His daughter Isabella succeeds.
1278 Death of Isabella’s husband Philip of Anjou. Guillaume de la Roche, duke of Athens, governs for ten years.