In the first years of the 13th century, already before the arrival of the Fourth Crusade in the Byzantine Empire, Argos and Nauplia became the centre of an independent domain under the Greek lord Leo Sgouros.

The Lord of Athens, Otto de la Roche (r. 1204–1225/34), played a major role in their capture, and as a reward the Prince of Achaea Geoffrey I of Villehardouin (r. 1209 – c. 1229) gave him Argos and Nauplia as a fief, along with an income of 400 hyperpyra from Corinth.

Much as happened elsewhere in the Morea, the local Greek magnates simply submitted to their new Frankish lords, but kept their possessions and Orthodox faith, as well as a typically Byzantine culture, as evidenced by the continued construction of Byzantine-style churches during the period.

[12] Following the fall of Boniface's Kingdom of Thessalonica to the Greek Despotate of Epirus in 1224, the Principality of Achaea emerged as the most powerful and pre-eminent among the Latin states of southern Greece.

Inevitably, the other Latin lordships began to be drawn into the orbit of Achaea, which during the early reign of William II of Villehardouin (r. 1247–1278) reached the height of its power and prosperity.

[14][16] At about the same time, William received from the Latin Emperor the suzerainty over the Duchy of Naxos, Negroponte (Euboea), and possibly over the Marquisate of Bodonitsa as well, while the County of Cephalonia also recognized his overlordship.

In its aftermath, the Catalans took over the Duchy of Athens and, with the military capacity of the remaining Latin states of Greece crippled, threatened to invade the Morea and take over Argos and Nauplia as well.

[26] Over the next few years, with support from the Angevin Kingdom of Naples and the Papacy, Joanna dispatched men and provisions to the Argolid, which was administered in her name by the local Frankish brothers Walter and Francis of Foucherolles.

Clement further ordered the Knights Hospitaller to provide three or four galleys and men to defend the Brienne lands, and in 1314 commanded all Templar properties in the Duchy of Athens to be placed under the control of Gaucher V de Châtillon and to be used against the Catalans.

[27][32] After 1321, Walter II repeatedly announced his intention to campaign in Greece and recover the Duchy of Athens, but financial constraints and his obligations to the King of Naples kept him occupied in Italy.

Sailing from Brindisi in August, Walter attacked first the Latin County palatine of Cephalonia and Zakynthos, and the Greek Despotate of Epirus, forcing them to recognize the overlordship of King Robert.

He had captured the island of Leucas and Vonitsa for himself and briefly restored Angevin suzerainty over western Greece, but the main objective had eluded him, and he had ended up with even more crippling debts.

[37] The increased threat to the lordship prompted Walter II to construct two new castles, which first appear in his will of 1347: at Kiveri (Chamires in French) across the Argolic Gulf from Nauplia and Thermisi (Trémis) further east along the coast, across Hydra Island.

[1][38] Despite the depredations from raids, the Brienne fief was relatively prosperous: the area was fertile and supported agriculture, pastures for livestock, and vineyards, while the Argolic Gulf provided fisheries and salt flats near Thermisi.

[40][41] Their rule proved unpopular, however, and in 1360 the local populace rebelled—according to historian Thanos Kondylis, perhaps with the encouragement of the Foucherolles—when Averardo de Medici increased taxation on figs and raisins, and blockaded Guy's soldiers in their castles.

The situation was resolved when Guy in person came and settled in the lordship—he is attested at Nauplia in December 1364, where he issued an act in favour of Jacomo, Lord of Tzoya and a son-in-law of Nicholas of Foucherolles.

[50] The marriage of Maria of Enghien and Pietro Cornaro coincided with an increasing Venetian interest in the region, as the Republic faced new challenges and opportunities in the Aegean with the rise of the Ottomans.

In the first years of their reign, they resided in Venice, and Pietro's father Federico acted on their behalf, securing permissions from the Venetian government to send supplies or arm a galley to defend the lordship.

Before the Venetians could arrive to take over the two towns, however, the Byzantine Despot of the Morea Theodore I Palaiologos (r. 1383–1407), and his ally and father-in-law Nerio I Acciaioli seized them with the aid of an Ottoman army under Evrenos.

[52][53][54] After Maria's death in 1393, her uncle Engelbert—who had originally received the lordship in 1356—claimed her inheritance, but when the Venetians provided the document of sale, and suggested that they would be willing to cede the castles if he could pay for their defence and reimburse Venice for the costs of their purchase and the ongoing siege of Argos, he dropped his claim.