Several sources suggest that Demetrius was the first Indo-Greek ruler to extend his conquests to the Indian subcontinent. By 182 BCE, he possessed Kapisa, Gandhara, and Western Punjab.
However, there is no evidence that Demetrius paid attention to the beliefs of his Buddhist subjects. Following Demetrius, a new branch of Greeks, led by Eucratides, emerged in Bactria.
The Indo-Greek rule in North-Western India saw internecine fighting among various princes of the Euthydemus and Eucratides houses. The latter did not favour Buddhism, some of the Euthydemid kings, like Menander I, were fervent sympathizers of Buddhism.
Menander I, described in the Pali work Milinda-panha, was a notable figure. He was a scholar and patron of Buddhism, with his capital at Sagala (Sakala), identified with Sialkot in the Punjab.
Menander's inquisitiveness about Buddhism is evident in the Milindapanha, reporting a dialogue in 'Sakala' between Menander and the Buddhist monk Nagasena. Menander expressed gratitude to Nagasena for resolving his doubts, becoming an upasaka, and even built a monastery, the 'Milinda-Vihara,' handing it over to Nagasena.
Some coins of Menander bear the epithet 'Savior,' suggesting his support for bhikshus and upasakas persecuted by the Pusyamitra Sunga.
Indian vassals, Viyakamitra and Vijayamitra, during Menander's time played a crucial role in society, ruling Indo-Iranian borderlands and professing Buddhism.
Indo-Greek vassal kings, like Meridarchs of Greek origin, also showed evidence of their Buddhist faith.