
45
FROM THE PERSIAN EMPIRE TO THE SASSANIANS
in Rome, the name Arsaces was used as a title by the fi rst 19 kings of 
Parthia, the majority of whom retained their personal names, and the 
dynasty is referred to as the Arsacid. Arsaces II made a treaty with the 
satrap of the neighboring and still rebellious province of Bactria, allow-
ing him to consolidate his authority and pursue expansion.
Parthian expansion was at the expense of the Seleucid Empire, as 
Arsaces II and the next three of his successors methodically picked 
off territory from the eastern satrapies. However, they were unable to 
defeat Seleucid power outright, especially during the reign of Antiochus 
the Great. During this period, Parthia was an autonomous state within 
the Seleucid Empire. It was the sixth Parthian king whom historians 
have credited with creating the Parthian Empire. Arsaces VI Mithridates 
(also known as Mithridates I and Mithridates the Great, r. ca. 171–138 
B.C.E.), the younger brother of his predecessor, Arsaces V Phraates, came 
to power at a conspicuous time in history as “one by one the provinces 
of Iran were lost to the Seleucids, and became a series of independent 
monarchies” (Colledge 1967, 28). Nevertheless, Mithridates bode his 
time for almost 11 years. In 160 
B.C.E., the Parthians overran Tapiura 
and Traxiane to the east, formerly Bactrian territory. He then turned 
westward, and by 147 
B.C.E., the Parthians occupied the ever-rebellious 
kingdom of Media. A few years later, Mithridates took a step that sig-
naled Parthian independence from Seleucid rule: He became the fi rst 
Parthian king to issue coinage.
The record next becomes somewhat hazy, but Mithridates returned 
east, “perhaps on account of an attack on his borders” (Colledge 1967, 
29). After further eastern conquest, he turned westward again with the 
intention of taking Babylonia as well as a few kingdoms, such as Elam 
and Armenia. This he swiftly accomplished, in 141 
B.C.E., but once 
again had to repel an invasion in the east—this time from Bactria. The 
Seleucid king, Demetrius II, took advantage of Mithridates’ preoccupa-
tion in the east to mount a counterattack to regain his lost territory. 
But Mithridates defeated the Bactrians, turned west for the third time, 
and defeated Demetrius, taking the Seleucid king prisoner. Demetrius 
thereupon forsook his throne but reclaimed it ca. 129 
B.C.E. and held it 
for another four years after that. Nevertheless, the Seleucid Empire was 
at a virtual end; the dynasty continued to rule until 64 
B.C.E. but had 
long since fallen back on Syria as its fi nal domain, where it served as a 
buffer state between the Parthian and the Roman Empires. Mithridates 
died in 138 
B.C.E., but the empire he founded continued to expand. 
By 113 
B.C.E., during the reign of Arsaces XI Mithridates (c. 124–87 
B.C.E.), upper Mesopotamia fell under Parthian sovereignty. This was