Complex sentence: The area of the Timiș river was not the land of the Hungarian royal tribe, and from the middle of the 10th century-the weakening of the royal rule-the local Slavic-Bulgarian tribes began to pursue a more and more independent foreign policy.
Split into simpler sentences: The area of the Timiș river was not the land of the Hungarian royal tribe. From the middle of the 10th century, when royal rule began weakening, the local Slavic-Bulgarian tribes began to pursue a more independent foreign policy.