They built the fortresses of Mystras , Passavas , Gustema ( Beaufort ) , and Great Maina .
After the Fourth Crusade in 1204 AD , Italian and French knights ( known collectively by the Greeks as Franks ) occupied the Peloponnese and created the Principality of Achaea .
knights built the fortresses of Mystras , Passavas , Gustema ( Beaufort ) , and Great Maina .
After the Fourth Crusade in 1204 AD , Italian and French knights ( known collectively by the Greeks as Franks ) occupied the Peloponnese and created the Principality of Achaea .