The bulk of the high nobility included the powerful Parthian noble families (known as the "wuzurgan") that were centered on the Iranian plateau. They served as the backbone of the Sasanian feudal army and were largely autonomous. The Sasanian shahs had noticeably little control over the "wuzurgan"; attempts to restrict their self-determination usually resulted in the murder of the shah. Ultimately, the Parthian nobility worked for the Sasanian shah for personal benefit, personal oath, and, conceivably, a common awareness of the "Aryan" (Iranian) kinship they shared with their Persian overlords.