Demetrius I of Bactria

Demetrius I "the Invincible" (Aniketos)
Greco-Bactrian/Indo-Greek king
Portrait of Demetrius I.
Reign	c. 200 – c. 180 BC
Predecessor	Euthydemus I
Dynasty	Euthydemid dynasty
Father	Euthydemus I
Religion	Buddhism, Hellenism

Demetrius I (Greek: Δημήτριος Α΄) was a Greek king (reigned c. 200–180 BC) of Gandhara. He was the son of Euthydemus and succeeded him around 200 BC, after which he conquered extensive areas in what is now Afghanistan and Pakistan, thus creating an Indo-Greek Kingdom far from Hellenistic Greece. He was never defeated in battle and was posthumously qualified as the Invincible (Aniketos) on the pedigree coins of his successor Agathocles. Demetrius I may have been the initiator of the Yavana era, starting in 186-185 BCE, which was used for several centuries thereafter.

"Demetrius" was the name of at least two, probably three Greek kings of Bactria. The much debated Demetrius II was a possible relative, whereas Demetrius III (c. 100 BC), is known only from numismatic evidence. Demetrius I was also known as the second Alexander.

The father of Demetrius, Euthydemus, was attacked by the Seleucid ruler Antiochus III around 210 BC. Although he commanded 10,000 horsemen, Euthydemus initially lost a battle on the Arius and had to retreat. He then successfully resisted a three-year siege in the fortified city of Bactra, before Antiochus finally decided to recognize the new ruler.

The final negotiations were made between Antiochus III and Demetrius. Antiochus III was reportedly highly impressed by the demeanour of the young prince, and offered him one of his daughters in marriage, around 206 BC:

The term used for "young prince" is neaniskos (νεανίσκος), suggesting an age around 16, which in turn gives a birth date for Demetrius around 222 BC.