Kavad's reign is noteworthy for his reforms, which he had been able to make with the nobility and clergy weakened by the Mazdakites. They were not be completed under his reign but were continued by his son, Khosrow I. The serious blows the Sasanians had suffered at the hands of the Hephthalites in the last quarter of the 5th-century was a key reason behind the reforms the two made. Tax reform was implemented, a poll tax was created, and a review of taxable land was undertaken to ensure taxation was fair. The empire was divided into four frontier regions ("kust" in Middle Persian), with a military commander ("spahbed") in charge of each district; a chancery was also added to keep the soldiers equipped. Before Kavad and Khosrow's reforms, the Iranians' general ("Eran-spahbed") managed the empire's army. Many of these military commanders were notably from the Parthian "wuzurgan", indicating the continuation of their authority, despite the efforts by Kavad and Khosrow. A new priestly office was also created known as the "advocate and judge of the poor" ("driyōšān jādag-gōw ud dādwar"), which assisted the clergy to help the poor and underprivileged (an obligation they had possibly ignored previously).