He was the son of the Greco-Bactrian Kingdom's ruler Euthydemus I and succeeded him around 200 BC, after which he conquered extensive areas in what is now southern Afghanistan, Iran and Pakistan and India.

[citation needed] In an inscription found in the Kuliab area of Tajikistan, in western Greco-Bactria, and dated to 200-195 BC,[7] a Greek by the name of Heliodotos, dedicating a fire altar to Hestia, mentions Euthydemus and Demetrius:[8][7]

τόνδε σοι βωμὸν θυώδη, πρέσβα κυδίστη θεῶν Ἑστία, Διὸς κ(α)τ᾽ ἄλσος καλλίδενδρον ἔκτισεν καὶ κλυταῖς ἤσκησε λοιβαῖς ἐμπύροις Ἡλιόδοτος ὄφρα τὸμ πάντων μέγιστον Εὐθύδημον βασιλέων τοῦ τε παῖδα καλλίνικον ἐκπρεπῆ Δημήτριον πρευμενὴς σώιζηις ἐκηδεῖ(ς) σὺν τύχαι θεόφρον[ι] "Heliodotos dedicated this fragrant altar for Hestia, venerable goddess, illustrious amongst all, in the grove of Zeus, with beautiful trees; he made libations and sacrifices, so that the greatest of all kings Euthydemos, as well as his son, the glorious, victorious and remarkable Demetrios, be preserved from all pains, with the help of Tyche with divine thoughts.

In the Paramparapustaka chronicle, Sri Lankan monks state that Brihadratha, the last Mauryan Emperor, married a daughter of Demetrius, Berenice.

[12] [13] Demetrius may have first started to recover the province of Arachosia, an area south of the Hindu Kush already inhabited by many Greeks but ruled by the Mauryas since the annexation of the territory by Chandragupta from Seleucus.

[citation needed] In his Parthian stations, Isidorus of Charax mentions a colony named Demetrias, supposedly founded by Demetrius himself: The Greek campaigns may have gone as far as the capital Pataliputra in eastern India (today Patna): It is generally considered that Demetrius ruled in Taxila (where many of his coins were found in the archaeological site of Sirkap).

[citation needed] The Indian records also describes Greek attacks on Saketa, Panchala, Mathura and Pataliputra (Gargi-Samhita, Yuga Purana chapter).

[16][17][18] Demetrius I died of unknown reasons, and the date 180 BC is merely a suggestion aimed to allow suitable regnal periods for subsequent kings, of which there were several.

Demetrius II left behind his generals Apollodotus and Menander, who in turn became kings of India and rulers of the Indo-Greek Kingdom following his death.

[citation needed] Geoffrey Chaucer names Demetrius among the combatants at a tournament held in Athens by Theseus: The grete Emetreus, the kyng of Inde, Upon a steede bay trapped in steel, Covered in clooth of gold, dyapred weel, Cam ridynge lyk the God of armes, Mars.

[citation needed] However, that persecution in turn is debatable, with contemporary historians such as Romila Thapar suggesting that some of the accounts might be the product of exaggeration from Buddhist missionaries.