In the mid-3rd century BCE, Arsaces I led the Parni to seize control in northeastern Iran, launching the Arsacid (Parthian) dynasty. This created a durable state positioned between the Mediterranean world and Central Asia. Parthia’s location would later make it a key broker for long-distance caravan trade.
Under Mithridates I, Parthia expanded westward and took major territories from the Seleucid Empire, including Mesopotamia. Controlling these river corridors and cities strengthened Parthia’s ability to tax and protect trade moving between West Asia and the Iranian plateau. This expansion set the stage for Parthia’s later role as a “middle zone” on Silk Road routes.
In 138 BCE, the Han court sent Zhang Qian to seek alliances and gather information in Central Asia. His reports helped show that travel and contact far to the west were possible, encouraging sustained diplomacy and trade. These connections helped form what later became known as Silk Road networks linking East Asia to West Asia and beyond.
In the late 120s BCE, Ctesiphon developed on the Tigris as a new Parthian center opposite the older Hellenistic city of Seleucia. Its river crossing and road connections made it well placed for caravans and for the movement of goods between Mesopotamia and Iran. Over time, Ctesiphon became one of the main hubs where long-distance trade could be organized and taxed.
Mithridates II’s reign (widely dated 123–88 BCE) is often treated as a high point in Parthian power. He restored order, expanded influence in multiple directions, and is strongly associated with tighter control over key borderlands and routes. A stronger Parthian state could more reliably regulate caravan passage and profit from transit trade across its territory.
Around 58 BCE, Ctesiphon became the Parthian capital, bringing the royal court closer to the empire’s western frontier. That shift helped Parthian rulers manage diplomacy and conflict with Rome, while also supervising trade traffic moving through Mesopotamia. As capital and commercial center, Ctesiphon linked state power with the practical business of taxing and protecting trade routes.
In 53 BCE, Parthian forces defeated a Roman army under Crassus near Carrhae using mobile cavalry and horse archers. The defeat halted Roman advances into Parthian Mesopotamia and reinforced the Euphrates region as a contested frontier. A more stable Parthian western boundary helped Parthia continue shaping the flow of East–West trade passing through its lands.
By the mid-1st century CE, merchants increasingly used Red Sea and Indian Ocean routes described in the Periplus of the Erythraean Sea. These sea routes could bypass parts of overland travel, changing how goods reached Roman markets. Even with maritime competition, Parthian-controlled land corridors and Mesopotamian centers still mattered for moving and redistributing high-value goods inland.
In 97 CE, the Han general Ban Chao sent Gan Ying west to learn about Da Qin (Rome). Gan Ying reached the far western edge of Parthian-controlled territory near a “western sea,” but did not continue onward. The episode reflects how Parthian geography—and local intermediaries—could shape what information and people moved between Rome and Han China.
In 116 CE, Roman forces under Emperor Trajan captured Ctesiphon, showing that warfare could directly threaten key Parthian commercial and administrative centers. Even when occupations were temporary, such raids disrupted security and raised the costs of moving goods. Repeated frontier wars pushed traders to adapt routes and increased the value of stable, well-guarded corridors.
In 197 CE, Emperor Septimius Severus sacked Ctesiphon, again damaging a central Parthian city tied to long-distance trade and government. Such attacks weakened confidence in overland security and strained Parthian resources. By the early 3rd century CE, internal rivalries and external pressure made it harder for Parthia to sustain its older role as a stable trade mediator.
On 28 April 224 CE, Ardashir I defeated the Parthian king Artabanus IV at the Battle of Hormozdgan. This ended Arsacid rule and began the Sasanian Empire, reshaping politics across Iran and Mesopotamia. The change in dynasty marked a clear turning point in how East–West routes were governed, taxed, and defended in late antiquity.
Parthian mediation of East–West trade routes (3rd century BCE–3rd century CE)