wood, uninhabited and untrodden. Pausanias also says that the island Sphacteria lies before the harbour of Pylos like Rheneia before the anchorage of Delos. A little later the Athenians captured a number of Spartan troops besieged on the adjacent island of Sphacteria (see Battle of Sphacteria). Spartan anxiety over the return of the prisoners, who were taken to Athens as hostages, contributed to their acceptance of the Peace of Nicias in 421 BC. Middle Ages Little is known of Pylos under Byzantine rule, except for a mention of raids by Cretan Saracens in the area c. 872/3. In the 12th century, the Muslim geographer al-Idrisi mentioned it as the "commodious port" of Irūda in his Nuzhat al-Mushtaq. In 1204, following the Fourth Crusade, the Peloponnese became the Principality of Achaea, a Crusader state. Pylos fell quickly to the Crusaders according to a brief reference in the Chronicle of the Morea, but it is not until the 1280s that it is mentioned again. According to the French and Greek versions of the Chronicle, Nicholas II of Saint Omer, the lord of Thebes, who in c. 1281 received extensive lands in Messenia in exchange for his wife's possessions of Kalamata and Chlemoutsi, erected a castle at Navarino. According to the Greek version, he intended this as a future fief for his nephew, Nicholas III, although the Aragonese version attributes the construction to Nicholas III himself, a few years later. According to A. Bon, a construction under Nicholas II in the 1280s is more likely, possibly in the period 1287–89 when he served as the viceroy (bailli) of Achaea. Despite Nicholas II's intentions, however, it is unclear whether his nephew did indeed inherit Navarino. If he did, it remained his until his death in 1317, when it and all the Messenian lands of the family reverted to the princely domain, as Nicholas III had no children. The fortress remained relatively unimportant thereafter, except for the naval battle in 1354 between Venice and Genoa, and an episode in 1364, during the conflict between Mary of Bourbon and the Prince Philip of Taranto, due to Mary's attempt to claim the Principality following the death of her husband, Robert of Taranto. Mary had been given possession of Navarino (along with Kalamata and Mani) by Robert in 1358, and the local castellan, loyal to Mary, briefly imprisoned the new Prince's bailli, Simon del Poggio. Mary retained control