Ottoman incursions into the Morea resumed under Turahan Bey after 1423. Despite the reconstruction of the Hexamilion wall at the Isthmus of Corinth, the Ottomans under Murad II breached it in 1446, forcing the Despots of the Morea to re-acknowledge Ottoman suzerainty, and again under Turahan in 1452 and 1456. Following the occupation of the Duchy of Athens in 1456, the Ottomans occupied a third of the Peloponnese in 1458, and Sultan Mehmed II extinguished the remnants of the Despotate in 1460. The last Byzantine stronghold, Salmeniko Castle, under its commander Graitzas Palaiologos, held out until July 1461. Only the Venetian fortresses of Modon, Coron, Navarino, Monemvasia, Argos and Nauplion escaped Ottoman control.