Diodotus I

Diodotus I Soter (Greek: Διόδοτος Σωτήρ, Diódotos Sōtḗr, "Diodotos the Savior"; c. 300 BC – c. 235 BC) was the first Hellenistic king of Bactria. Diodotus was initially satrap of Bactria, but became independent of the Seleucid empire around 255 BC, establishing the Greco-Bactrian Kingdom. In about 250 BC, Diodotus repelled a Parthian invasion of Bactria by Arsaces. He minted an extensive coinage and administered a powerful and prosperous new kingdom. He died around 235 BC and was succeeded by his son Diodotus II.

His rule was recounted by Apollodorus of Artemita in the Parthian History, but this text is lost, and surviving literary sources only mention him in passing. Thus, most details of Diodotus' life have to be reconstructed from numismatics and brief references by Justin and other historians.

The region of Bactria, which encompassed the Oxus river Valley in modern Afghanistan and Tajikistan, was conquered by Alexander between 329 and 327 BC and he settled a number of his veterans in the region. In the wars which followed Alexander's death in 323 BC, the region was largely left to its own devices, but it was incorporated in the Seleucid empire by Seleucus I between 308 and 305 BC, along with the rest of the territories that Alexander had conquered in Iran and Central Asia. Seleucus entrusted the region to his son and co-regent, Antiochus I, around 295 BC. Between 295 and 281 BC, Antiochus I established firm Seleucid control over the region. The region was divided into a number of satrapies (provinces), of which Bactria was one. Antiochus founded or refounded a number of cities on the Greek model in the region and he opened a number of mints to produce coinage on the Attic weight standard. After Antiochus I succeeded his father as ruler of the Seleucid empire in 281 BC, he entrusted the east to his own son, Antiochus II, who remained in this position until he in turn succeeded to the throne in 261 BC.

Diodotus became Seleucid satrap of Bactria during Antiochus II's reign. The nature of the Bactrian satrapy, traditionally assigned to an Achaemenid Crown Prince, suggests Diodotus' prominence. According to some scholars, he may have later married a daughter of Antiochus II (as his second marriage); although this is uncertain and Tarn's genealogical assertions are controversial. The Babylonian Astronomical Diaries record that an unnamed Bactrian satrap sent a herd of twenty war elephants to Babylon at the beginning of 273 BC to join the Seleucid forces fighting against Ptolemaic Egypt in the First Syrian War. This satrap may have been Diodotus, or a predecessor. Archaeological evidence for the period comes largely from excavations of the city of Ai-Khanoum, where this period saw the expansion of irrigation networks, the construction and expansion of civic buildings, and some military activity, probably raiding by nomads from the Central Asian steppe. As satrap, Diodotus was probably involved in these matters, though the specifics are not recoverable.

At some point, Diodotus seceded from the Seleucid empire, establishing his realm as an independent kingdom, known in modern scholarship as the Graeco-Bactrian kingdom. The event is mentioned briefly by the Roman historian Justin:

Diodotus, the governor of the thousand cities of Bactria, defected and proclaimed himself king; all the other people of the Orient followed his example and seceded from the Macedonians [i.e. the Seleucids].

— Justin Epitome of Pompeius Trogus 41.4

The date of this event is unclear. The literary evidence is as follows: