Nerio I Acciaioli in the context of "Lordship of Argos and Nauplia"

During the late Middle Ages, the two cities of Argos (Greek: Άργος, French: Argues) and Nauplia (modern Nafplio, Ναύπλιο; in the Middle Ages Ἀνάπλι, in French Naples de Romanie) formed a lordship within the Frankish-ruled Morea in southern Greece.

Following their conquest in 1211–1212, the cities were granted as a fief to Otto de la Roche, duke of Athens, by Geoffrey I of Villehardouin, prince of Achaea. The lordship remained in the possession of the de la Roche and the Brienne dukes of Athens even after the conquest of the Duchy of Athens by the Catalan Company in 1311, and the Brienne line continued to be recognized as dukes of Athens there. Walter VI of Brienne was largely an absentee lord, spending most of his life in his European domains, except for a failed attempt in 1331 to recover Athens from the Catalans. After his death in 1356 the lordship was inherited by his sixth son, Guy of Enghien. Guy took up residence in Greece, and in 1370–1371 Guy and his brothers launched another, also failed, invasion of the Catalan domains. When Guy died in 1376, the lordship then passed to his daughter Maria of Enghien and her Venetian husband Pietro Cornaro, who would also reside there until his death in 1388. The lordship became a de facto Venetian dependency during this period, and shortly after his death, Maria sold the two cities to Venice, where she retired. Before Venice could take possession, Argos was seized by the Despot Theodore I Palaiologos, while his ally, Nerio I Acciaioli seized Nauplia. The latter city was soon captured by Venice, but Argos remained in Byzantine hands until 1394, when it too was handed over to Venice.

The Duchy of Neopatras (Catalan: Ducat de Neopàtria; Sicilian: Ducatu di Neopatria; Greek: Δουκάτο Νέων Πατρών; Latin: Ducatus Neopatriae) was a principality in southern Thessaly, established in 1319. Officially part of the Kingdom of Sicily, itself part of the Crown of Aragon, the duchy was governed in conjunction with the neighbouring Duchy of Athens, it enjoyed a large degree of self-government. From the mid-14th century, the duchies entered a period of decline: most of the Thessalian possessions were lost to the Serbian Empire, internal dissensions arose, along with the menace of Turkish piracy in the Aegean and the onset of Ottoman expansion in the Balkans. Enfeebled, the Catalan possessions were taken over by the Florentine adventurer Nerio I Acciaioli in 1385–1390. The title of Duke of Neopatras was held by the heir of the King of Sicily.