The Sassanid Empire was an empire that existed in modern-day Persia and Central Asia. Although at first existing as a secular nation, it eventually became filled with Zoroastrian extremism following weakening and defeats at the hand of the Tang. This period of religious extremism continued for five hundred years until the rise of the Mongol Empire. Despite its persecution of minorities, the nation brought power to Persia that was unseen after the fall of the Achaemenids and is fondly remembered by modern Persians as a golden era of Persian society. The empire is also notable for ending Islamic expansion eastwards.