Conversation so far:
Who ruled over the Assyrian homeland in the Middle Ages?
Following the Arab Islamic conquest of Mesopotamia in the 7th century Assyrian Christians throughout the Middle Ages were subjected to Arabizing superstrate influence.
Who did the Rashidun Caliphate have to defeat to rule over Mesopotamia?
Arab Muslims first attacked Sassanid Empire territory in 633.

Question: Who else ruled the region during the middle ages ?
Self-contained rewrite: Who else ruled Mesopotamia during the Middle Ages besides the Rashidun Caliphate?