From the mid 8th-mid 11th century the political power and cultural development of Christian Nubia peaked. In 747 Makuria invaded Egypt, which at this time belonged to the declining Umayyads, and it did so again in the early 960s, when it pushed as far north as Akhmim. Makuria maintained close dynastic ties with Alodia, perhaps resulting in the temporary unification of the two kingdoms into one state. The culture of the medieval Nubians has been described as "''Afro-Byzantine''", but was also increasingly influenced by Arab culture. The state organisation was extremely centralised, being based on the Byzantine bureaucracy of the 6th and 7th centuries. Arts flourished in the form of pottery paintings and especially wall paintings. The Nubians developed an own alphabet for their language, Old Nobiin, basing it on the Coptic alphabet, while also utilizing Greek, Coptic and Arabic. Women enjoyed high social status: they had access to education, could own, buy and sell land and often used their wealth to endow churches and church paintings. Even the royal succession was matrilineal, with the son of the king's sister being the rightful heir.