Shahpur I was the king from 240 to 271 CE. He was the son and successor of Ardeshir was crowned emperor at Ctesiphon on 20th March, 240 CE. For the first two years, he co-ruled with his father. At the time of coronation, as per the tradition, he gave an admonition in presence of his council of ministers comprising of wise men, elders and priests. He assured the council that he will follow the policies of his father in all matters, including collecting only three percent tax from his people. He continued the conquests and expansion of the empire.
Soon after becoming the king, Shahpur stormed the defenses of the city of Hatra, which had proved to be a bugbear not only to his father but also to Romans. Then he captured the fortress city of Nisibis, followed by Antioch and Carrhae.
In 243 CE, the Roman emperor Gordianus III came with an army of Goth and German soldiers, successfully defeated Shahpur and took control of the cities of Mesopotamia, Nisibis, Antioch and Carrhae.
However, in a later war in 244, Shahpur defeated and killed Gordianus, at Misikhe near Ctesiphon close to the Euphrates river. There he established a city called Firoz-Shahpur “Victorious Shahpur”.
The next Roman Caesar was Philip the Arab (244-253), who was a soldier-emperor. He instigated the provinces upto Kaydafah in North Africa against the Iranians. Then the Caesar and Roman army under the leadership of General Belisarius (Bazanush), set off to attack the Iranians. The Iranian army under commander Kersasp went to defend, and met the Romans at Paluniyah.
In 252, a bloody battle was fought in which thousands of Romans were killed and seventy thousand were taken prisoners. The Romans were badly defeated. The Caesar of Rome asked for truce by ceding the territories of Armenia and Mesopotamia and paying him five lakh denarii as tax. Shahpur waited at the battle camp till the taxes arrived with several other gifts. However, Philip reneged on the peace treaty and attacked again. Shahpur was prepared for the attack and conclusively defeated him in 253. To celebrate this victory, he established the city of Nishāpur.
Valerian (253-260), the next Roman Caesar, was keen to destroy Shahpur. However he miscalculated the massive might of the Sasanians. After some preliminary victories, Valerian was crushed by Shahpur in 260 in the battle of Edessa. Valerian was captured along with seventy thousand Roman soldiers. Never in the history of Rome, had a Roman emperor been captured alive. It was one of the most humiliating military losses in Roman history. To celebrate this conclusive victory Shahpur built a city called Shahpur-gard close to the site of victory. He also established a city to house the Roman prisoners of wars. The Roman Caesar Valerian was also detained along with the other prisoners.
While returning, the Sasanian and Roman armies passed the city of Shustar in the province of Khuzistan, where they had great difficulty in crossing the river Karun. Shahpur in his wisdom asked Valerian to make use of the Roman ingenuity in engineering and wealth from Iranian treasures. He entrusted him the task of building a dam-bridge on the river Karun with the help of the captured soldiers. Shahpur assured him that he will be released once he completed this task. It is said that Valerian took three years and made a beautiful bridge which stands even today and is known as Band-e-Kaisar.
Valerian was kept a prisoner for some time. Even today, in the ruins of the city of Bishāpur lies a place marked Zindān-e-Valerian “Valerian’s prison”. What happened to Valerian in the end is not conclusively known. Some believe, he met with his end in Iran. Others maintain that Valerian was honourably allowed to return to Rome.
Thus Shahpur became the one and only emperor in world history who defeated three successive Roman Caesars, killing one, making another a tributary, and the unprecedented achievement of capturing and taking the third as a prisoner.
Religion was always given a lot of importance by Ardeshir, and his son Shahpur was no different. The chief Zoroastrian priest during his time was Kartir, who tried to establish standard and uniform Zoroastrian religious laws which were quite strict and stringent. He made an attempt to put in writing the scattered Avesta Nasks. He also tried to establish the superiority of the priests over the rulers. Kartir remained a very influential figure in Sasanian history and remained the religious head for several successive Sasanian kings.
Mithraism was prevalent is Shahpur’s time and was popular among Sasanian and Roman troops. In fact, the movement started in 100 CE and lasted till 400 CE. It was at its zenith during this period and was spread all over Europe into the Balkans, Italy and England.
We come to know from sources other than Firdausi, that in the reign of Shahpur emerged a heretic by the name Māni. He was born in 216 to Iranian parents and believed to have visions since the age of four. He was a good orator, and he claimed to be a prophet. When Māni was about twenty, he had a spiritual vision, and he came forward as a new prophet.
His philosophy was a synthesis of various existing religions like Zoroastrianism, Hinduism, Buddhism and Christianity, and hence not confined by national borders. Initially his teachings were well received. Māni claimed that Hormazd and Ahreman were equals. He identified evil with matter and good with spirit. His dietary laws forbid the eating of animal products. There was an antipathy towards sexual activity. Zoroastrian and Christian priests vehemently opposed his stand. He could not substantiate his arguments in the debates that ensued.
Mani was introduced to the king Shapur I by prince Peroz. The king was duly impressed by him and made him an honorary member of the court, where he started to preach his doctrine.
Opposition to Mani’s views grew stronger and at last Shahpur had to advise Mani to leave the country. Mani left Iran for many years, and wandered all over Central Asia, including Syria, Palestine and Egypt. He even went as far east as China. Manichaeism spread towards the east into Spain, Greece, Illyria, Italy and Gaul. So vast was his influence that his works were found extensively in Sogdian, Old Turkish and Chinese. A Turkish king officially endorsed Manichaeism as the state religion.
After the death of Shahpur I in May 272 CE, Mani returned to Iran and was well-received by Shahpur’s successor Hormazd I, but when Hormazd died after a very short reign, his successor, Bahram I, showed strong dislike for Mani. His head priest Kartir tortured Mani and put him to death in 276. Mani’s followers were banned throughout the Iranian Empire, and hence they migrated to the west and south. Mani’s faith continued in the East till about the 17th century CE. Shahpur I has commemorated his victories over the three Roman emperors in one single consolidated rock relief at Nakhsh-i-Rustom, in one of the most majestic and well-preserved reliefs. In fact, this place got its name from this relief where the majestic looking king Shahpur I was mistaken for the great warrior Rustom. Nearby, at Kābā-i-Zardusht, Shahpur I has also left a long description of his conquests which is the first long testament by a Sasanian king.