Conflicting accounts shroud the details of the fall of the Parthian Empire and subsequent rise of the Sassanid Empire in mystery.

One Babak, a descendant of a line of the priests of the goddess Anahita, was originally the ruler of a region called Kheir.

However, by the year 200, he had managed to overthrow Gocihr, and appoint himself as the new ruler of the Bazrangids.

His mother, Rodhagh, was the daughter of the provincial governor of Persis.

Babak and his eldest son Shapur managed to expand their power over all of Persis.

The subsequent events are unclear, due to the sketchy nature of the sources.

It is certain, however, that following the death of Babak, Ardashir, who at the time was the governor of Darabgird, got involved in a power struggle of his own with his elder brother Shapur.

Sources reveal that Shapur, leaving for a meeting with his brother, was killed when the roof of a building collapsed on him.

By the year 208, over the protests of his other brothers who were put to death, Ardashir had declared himself ruler of Persis.

Once Ardashir was appointed Shahenshah, he had moved his capital further to the south of Persis and founded Ardashir-Khwarrah (formerly Gur, modern day Firuzabad), constructing several great palaces and carving rock reliefs.

The city, well supported by high mountains and easily defendable through narrow passes, has become the center of Ardashir's efforts to gain more power.

The city is surrounded by a high, circular wall, probably copied from that of Darabgird, and on the north-side includes a large palace, remains of which still survive today.

After establishing his rule over Persis, Ardashir I has rapidly extended his territory, demanding fealty from the local princes of Fars, and gaining control over the neighboring provinces of Kerman, Isfahan, Susiana and Mesene.

This expansion quickly comes to the attention of Artabanus IV, the Parthian king, who initially orders the governor of Khuzestan to wage war against Ardashir in 224, but the battles are victories for Ardashir.

Sassanid ruler Ardashir I, a king of kings, in a complete reversal of the Parthian form of governance, has centralized power in his hands.

Ardashir is an energetic king, responsible for the resurgence not just of Persia but of Iranian-speaking peoples as a unified nation (ethnous as it appears in the Greek version of his successor's inscription on the Ka'ba-ye Zartosht), the strengthening of Zoroastrianism, and the establishment of a dynasty that will endure for four centuries.

Ardashir has constructed massive building projects in Fars province as a proclamation of imperial grandeur.

While his campaigns against Rome have met with only limited success, he has achieved more against them than the Parthians had done in many decades and has prepared the way for the substantial successes his son and successor Shapur I, who accedes to the throne first as co-ruler and then sole ruler following his father’s death in 242, will enjoy against the same enemy.

Shapur I, an ambitious organizer and statesman, had in 240 or 241 become the Persian king of the Sassanian dynasty founded by his father: he has united his empire by bringing the Iranian lords into line and by protecting the Zoroastrian religion.

He also tolerates the Manichaeans and puts an end to the persecutions of the Christians and Jews, thereby gaining the sympathy of these communities.

Roman Emperor Hadrian had fixed the frontiers at the Euphrates, but under Nero, the Romans had claimed control over the kings of Armenia, and under Caracalla, they had annexed Osroëne and Upper Mesopotamia.

The Parthian empire had been weak and often troubled, but the Sassanids are more dangerous.