Right up to the end of the 13th century Venice continued to practise her policy of commercial expansion: in the Mediterranean this was through acquiring and defending strategical trade route ports, whereas in the hinterland a series of fiscal privileges (exemption from excise duties etc.) was introduced for the main North Italian river and road networks. Venice then surrounded herself with a series of buffer states ruled by families noted for their rank or better for their inclination and capacity to use arms; such families included the Scaligers, the Carrarresi, the Estensi and the Gonzagas. In the Mediterranean the same role was delegated both to independent principalities of the Peloponnese and to Arab ones on the African coast.