was an Iranian significant political and cultural power in the ancient Near East and a counterweight to the Roman Empire in the region. Its ruling dynasty was founded by Arsace
Arsacids followed a vassalary system, which they adopted from the Seleucids. The Arsacid Empire was thus not a single coherent state, but instead made up of numerous tributary (but otherwise independent) kingdoms.

Root of the Persian Empire

In early 53 BCE, an ambitious Roman commander, Marcus Licinius Crassus, sought to invade Mesopotamia. He and his army walked into a trap set for them by the Parthian commander Surena, and in the resultant Battle of Carrhae roughly one half of the Roman army of about 40,000 men – including Crassus and his son – were killed. Of the remaining 20,000 men, 10,000 were made captive and only 10,000 were able to escape. The Arsacids did not capitalize on their victory, and Surena was himself executed by Orodes II.

In late 41 BCE or early 40 BCE, the Arsacid army under the command of Pacorus (son of Orodes II) and Quintus Labienus (who had defected to the Arsacids following the defeat of the Republicans in the Roman civil war) attacked the Romans. The expeditions were initially successful; Pacorus took Syria and Judea, while Labienus occupied large parts of Asia Minor. In 39 BCE, the Romans counterattacked, defeating both Labienus and Pacorus and killing both.

Economy ~ Asian 'silk Road'

The 138–126 BC travels of Zhang Qian to the West, Mogao Caves, 618–712 AD mural.

The Chinese explorer Zhang Qian, who visited the neighbouring countries of Bactria and Sogdiana in 126 BC, made the first known Chinese report on Parthia. In his accounts Parthia is named "Ānxī" (Chinese: 安息), a transliteration of "Arsacid", the name of the Parthian dynasty. Zhang Qian clearly identifies Parthia as an advanced urban civilization that farmed grain and grapes, made silver coins and leather goods;^[6] Zhang Qian equates the level of advancement of Parthia to the cultures of Dayuan (in Ferghana) and Daxia (in Bactria).

Anxi is situated several thousand li west of the region of the Great Yuezhi (in Transoxonia). The people are settled on the land, cultivating the fields and growing rice and wheat. They also make wine out of grapes. They have walled cities like the people of Dayuan (Ferghana), the region contains several hundred cities of various sizes. The coins of the country are made of silver and bear the face of the king. When the king dies, the currency is immediately changed and new coins issued with the face of his successor. The people keep records by writing on horizontal strips of leather. To the west lies Tiaozhi (Mesopotamia) and to the north Yancai and Lixuan (Hyrcania).

—Zhang Qian, trans. Burton Watson,Shiji, 123,