During the late Middle Ages, the two cities of Argos and Nauplia formed a lordship within the Frankish-ruled Morea in southern Greece.

Nerio I Acciaioli or Acciajuoli was the de facto Duke of Athens from 1385 to 1388, after which he reigned uncontested until his death in 1394. Born to a family of Florentine bankers, he became the principal agent of his influential kinsman, Niccolò Acciaioli, in Frankish Greece in 1360. He purchased large domains in the Principality of Achaea and administered them independently of the absent princes. He hired mercenaries and conquered Megara, a strategically important fortress in the Duchy of Athens, in 1374 or 1375. His troops again invaded the duchy in 1385. The Catalans who remained loyal to King Peter IV of Aragon could only keep the Acropolis of Athens, but they were also forced into surrender in 1388.