Under Parthian and Sassanian Iranian empires, scholars concentrated on exchanging knowledge and inventions by the countries around them – India, China, and the Roman Empire, when it is thought to be expanded over the other countries.

Beyond the frontiers, he secured the Empire with a buffer region of client states, and made peace with the Parthian Empire through diplomacy.

By 150 BC, Assyria was under the control of the Parthian Empire as Athura ( the Parthian word for Assyria ) where the Assyrian city of Ashur seems to have gained a degree of autonomy, and temples to the native gods of Assyria were resurrected.

It became part of the Parthian Empire in 167 BC.

Near the end of his life, Caesar began to prepare for a war against the Parthian Empire.

During his reign, the Empire defeated a revitalized Parthian Empire ; Aurelius ' general Avidius Cassius sacked the capital Ctesiphon in 164.

During his reign, the redoubtable general Corbulo conducted a successful war and negotiated peace with the Parthian Empire.

Following the decline of the central Parthian authority after clashes with the Roman Empire, a local Parthian leader, Gondophares established the Indo-Parthian Kingdom in the 1st century CE.

Following the fall of Achaemenid Empire, and after the fall of the Parthian Empire, the Sassanid empire ruled the northern half and at times the southern half of the Persian Gulf.

In the classical period, the city states of Mosylon, Opone, Malao, Sarapion, Mundus, and Tabae in Somalia developed a lucrative trade network connecting with merchants from Phoenicia, Ptolemic Egypt, Greece, Parthian Persia, Sheba, Nabataea and the Roman Empire.

Soon after however, a Parthian tribal chief called Arsaces invaded the Parthian territory around 238 BC to form the Arsacid Dynasty — the starting point of the powerful Parthian Empire.

* Parthian Empire

After solidifying his rule over the western provinces, Severus waged another brief, more successful war in the east against the Parthian Empire, sacking their capital Ctesiphon in 197 and expanding the eastern frontier to the Tigris.

The following year he led another, more successful campaign against the Parthian Empire, reportedly in retaliation for the support given to Pescennius Niger.

The Parthian capital Ctesiphon was sacked by the legions and the northern half of Mesopotamia was annexed to the Empire.

For another 400 years, until AD 410, the Kushan Empire was a major power in the region along with the Roman Empire, the Parthian Empire and the Han Empire ( China ).

The Persians had inherited a rich architectural legacy from the earlier Persian dynasties, and they started incorporating elements from earlier Parthian and Sassanid palace-designs into their mosques, influenced by buildings such as the Palace of Ardashir and the Sarvestan Palace.

By this time, the entire Iranian Plateau had been lost to Parthian control.

The following year was devoted to suppressing Mesopotamia and other Parthian vassals who had backed Niger.

The greater part of it remained in force, even through the Persian, Greek and Parthian conquests, which had little effect on private life in Babylonia ; and it survived to influence Romans.

King Mithradates had kept Demetrius II alive and even married him to a Parthian princess named Rhodogune, with whom he had children.

Perhaps the distinctions between dragons of western origin and Chinese dragons are arbitrary, since the later Roman dragon was certainly of Iranian origin: in the Roman Empire, where each military cohort had a particular identifying signum, ( military standard ), after the Parthian and Dacian Wars of Trajan in the east, the Dacian Draco military standard entered the Legion with the Cohors Sarmatarum and Cohors Dacorum ( Sarmatian and Dacian cohorts )— a large dragon fixed to the end of a lance, with large gaping jaws of silver and with the rest of the body formed of colored silk.

Before the end of the year, however, Roman forces had moved north to occupy Dausara and Nicephorium on the northern, Parthian bank.

The new Parthian ruler, Phraates II, had not been idle ; raising a new army while stirring up rebellion in the Seleucid occupied towns of Media.

The Seleucid empire had been disintegrating in the face of the Seleucid – Parthian wars and in 129 BCE Antiochus VII Sidetes was killed in Media by the forces of Phraates II of Parthia, permanently ending Seleucid rule east of the Euphrates.

After the death of Mithridates II of Parthia in 88 BCE, Tigranes took advantage of the fact that the Parthian Empire had been weakened by Scythian invasions and internal squabbling:

After Achaemenids had the region under their dominion ; in the Parthian and Sassanid eras Kirkuk was capital of Beth Garmai.

The Church of the East developed from the early Assyrian Christian communities in the Assuristan province of the Parthian Empire, and at its height had spread from its Mesopotamian heartland to as far as China and India.

Under Nero, the Romans fought a campaign ( 55 – 63 ) against the Parthian Empire, which had invaded the kingdom of Armenia, allied to the Romans.

With the Parthian threat still present, Bibulus sent two of his sons to Egypt in 50 BC to demand the recall of the Roman soldiers who had settled there, but were killed by the soldiers who refused to march.

By year ’ s end, Cassius had travelled to the south and crossed Mesopotamia at its narrowest point and proceeded to attack the twin Parthian cities on the Tigris river, Seleucia on the right bank, and Ctesiphon, the Parthian capital, on the left.

In the Parthian period, between 100 BC and 270 AD, the city becomes an important administrative centre of Parthian ruled Assyria ( Assuristan ), and some Assyriologists such as Simo Parpola have suggested it may have had some degree of autonomy or outright independence.

The Arsacid emperor Mithridates II ( c 123 – 88 / 87 BCE ) had scored many successes against the Scythians and added many provinces to the Parthian empire, and apparently the Scythian hordes that came from Bactria were also conquered by him.

Dynasties of Parthian or Persian descent, such as the Mihranids had come to rule the territory during Sassanian times.

By 63 BC / BCE, the partially Hellenized territory had come under Roman imperial rule as a valued crossroads to trading territories and buffer state against the Parthian Empire.

For the remaining duration of the Armenian kingdom, Rome still considered it a client kingdom de jure, but the ruling dynasty was of Parthian extraction, and contemporary Roman writers thought that Nero had de facto yielded Armenia to the Parthians.

Under Nero, the Romans fought a campaign ( 55 – 63 ) against the Parthian Empire, which had invaded the Kingdom of Armenia, allied with the Romans.

Considered to be an usurper and tyrant, he was overthrown in a rebellion supported by the Parthian Empire.

* The governor of Syria, Avidius Cassius, one of Lucius Verus ' generals, crosses the Euphrates and invades Parthian territory.

The Roman general Avidius Cassius captured Ctesiphon in 164 during another Parthian war, but abandoned it when peace was concluded.

The legion, with the others, cut off Cassius ' head, and sent it to Aurelius, who interestingly, let the legions be, just sending them back to their proper posts to watch the Parthian Empire.

The testudo was not invincible, as Cassius Dio also gives an account of a Roman shield array being defeated by Parthian cataphracts and horse archers at the Battle of Carrhae:

According to the Roman historian Cassius Dio, Pacorus sold the kingdom of Osroene to Abgar VII, and according to Ammianus Marcellinus he enlarged the Parthian capital Ctesiphon and built its walls.