Coin depicting the Greco-Bactrian king Euthydemus (230-200 B.C.) [Source]

Euthydemus was allegedly a native of Magnesia and possible Satrap of Sogdiana, who overturned the dynasty of Diodotus of Bactria and became a Greco-Bactrian king in about 230 BC according to Polybius. Strabo, on the other hand, correlates his accession with internal Seleucid wars in 223/221 BC.

Little is known of his reign until 208 BC when he was attacked by Antiochus III the Great, whom he tried in vain to resist on the shores of the river Arius, the modern Herirud. Although he commanded 10,000 horsemen, Euthydemus initially lost a battle on the Arius [1] and had to retreat. He then succesfully resisted a two-year siege in the fortified city of Bactra, before Antiochus finally decided to recognize the new ruler, and to offer one of his daughters to Euthydemus's son Demetrius around 206 BC [2].

Classical accounts also relate that Euthydemus negotiated peace with Antiochus III by suggesting that he deserved credit for overthrowing the original rebel Diodotus, and that he was protecting Central Asia from nomadic invasions thanks to his defensive efforts:

"...for if he did not yield to this demand, neither of them would be safe: seeing that great hords of Nomads were close at hand, who were a danger to both; and that if they admitted them into the country, it would certainly be utterly barbarised." (Polybius, 11.34).

The war lasted altogether three years. Following the departure of the Seleucid army, the Bactrian kingdom seems to have expanded. In the west, areas in north-eastern Iran may have been absorbed, possibly as far as into Parthia, whose ruler had been defeated by Antiochus the Great. These territories possibly are identical with the Bactrian satrapies of Tapuria and Traxiane.

His death has been estimated to about 200 BC.

There exist many coins of Euthydemus, portraying him as a young, middle-aged and old man. Some of them could be memorative issues by his son and a later king, Agathocles. The attribution of some of his coins (the younger portraits) to a second Euthydemus has been suggested but the evidence is very vague. The end of his reign can not be fixed, but he was succeeded by Demetrius, who went on to conquer northern India.