Khosrau I
Mazdakism was viewed by the Zoroastrian hierarchy as a heresy and its followers were persecuted by Zoroastrian Sassanian leaders. The Sassanian ruler Khosrau I launched a campaign against the Mazdakis in 524 or 528, culminating in a massacre which killed most of them, including Mazdak himself and restored orthodox Zoroastrianism as the state religion.