The Indo-Greeks practiced numerous religions during the time they ruled in the northwestern Indian subcontinent from the 2nd century BCE to the beginning of the 1st century CE. In addition to the worship of the Classical pantheon of the Greek deities found on their coins (e.g., Zeus, Herakles, Athena, Apollo), the Indo-Greeks were involved with local faiths, particularly with Buddhism, but also with Hinduism and Zoroastrianism.
Buddhism
After the Greco-Bactrians militarily occupied parts of northern India from around 180 BCE, numerous instances of interaction between Greeks and Buddhism are recorded.
The conversion of Menander
Menander I, the "Saviour king", is documented to have converted to Buddhism, and is described in Buddhist texts as a great benefactor of the religion. Menander, appears to have proselytized the faith through his domain similar to the Mauryan Ashoka and the future Kushan emperor Kanishka. He is famous for his dialogues with the Buddhist monk Nagasena, transmitted to us in the Milinda Panha, which explain that he became a Buddhist arhat:
Another Indian writing, the Stupavadana of Ksemendra, mentions in the form of a prophecy that Menander will build a stupa in Pataliputra.Stupavadana, Chapter 57, v15. Quotes in E.Seldeslachts.
Plutarch also presents Menander as an example of benevolent rule, and explains that upon his death, the honour of sharing his remains was claimed by the various cities under his rule, and they were enshrined in "monuments" (μνημεία, probably stupas), in a parallel with the historic Buddha:
The Butkara stupa was "monumentalized" by the addition of Hellenistic architectural decorations during Indo-Greek rule in 2nd century BCE."De l'Indus a l'Oxus: archaeologie de l'Asie Centrale", Pierfrancesco Callieri, p212: "The diffusion, from the second century BCE, of Hellenistic influences in the architecture of Swat is also attested by the archaeological searches at the sanctuary of Butkara I, which saw its stupa "monumentalized" at that exact time by basal elements and decorative alcoves derived from Hellenistic architecture".
Some Buddhist inscriptions also mention the name of Menander, suggesting intense Buddhist activity under his sponsorship:
Buddhist proselytism There are records of the involvement of Greeks in Buddhist pilgrimages. During the reign of Menander, the Greek (Pali: Yona, lit: "Ionian") Buddhist monk Mahadhammarakkhita (Sanskrit: Mahadharmaraksita, lit. "Great protector of the Dharma") is said to have come from Alasandra (thought to be Alexandria of the Caucasus, the city founded by Alexander the Great, near today's Kabul) with 30,000 monks for the foundation ceremony of the Maha Thupa ("Great stupa") built by king Dutthagamani at Anuradhapura in Sri Lanka around 130 BCE, indicating the importance of Buddhism within Greek communities in northwestern India, and the prominent role Greek Buddhist monks played in them:
Several Buddhist dedications by Greeks in India are recorded, such as that of the Greek meridarch (civil governor of part of a province) named Theodorus, describing in Kharoshthi how he enshrined relics of the Buddha. The inscriptions were found on a vase inside a stupa, dated to the reign of Menander or one of his successors in the 1st century BCE (Tarn, p391):
Although the spread of Buddhism to Central Asia and Northern Asia is usually associated with the Kushans, a century or two later, there is a possibility that it may have been introduced in those areas from Gandhara "even earlier, during the time of Demetrius and Menander".Puri, 1987: p. 19. There is however some textual evidence to suggest that Buddhism had penetrated much earlier to Central Asia, at least in a limited form: the first two disciples of the Buddha were named Tapassu and Bhallika, from the region of Balhika (the present Balkh, and Sanskrit for Bactria), and though it cannot necessarily be presumed that any extensive prosyletization occurred on their return journey, that the Sanskrit name for Bactria derived from the name of a Bactrian-Buddhist disciple is suggestive of some early influence. Bhallika and Tapassu were both travellers, and if nothing else, the story of their conversion and their home region's Sanskrit nomenclature illustrates the possibility of early transmission via the local trade routes.
Buddhist symbolism
From around 180 BCE, Agathocles and Pantaleon, probable successors to Demetrius I in the Paropamisadae, and the earliest Greek kings to issue Indian-standard square bilingual coins (in Brahmi), depicted the Buddhist lion together with the Hindu goddess Lakshmi.
Some coins of Agathocles in the Indian standard also show a six-arched stupa and a tree in a railing, typical symbol of the Bodhi tree in early Buddhism."Distinctively Indian religious types seems to occur on the coins struck by two of the Greek princes- "the tree in railing" and the "Chaitya" on certain coins of Agathocles and the "Wheel" which has been reasonably idenditfied with "the wheel of the Law" (Dharma-chakra) of Buddhism, on one of the numerous currencies of Menander" Hellenism in ancient India, Banerjee, p136 These coins show an unprecedented willingness to adapt to every aspect of the local culture: shape of the coinage, coinage size, language, and religion.
Later, some Indo-Greek coins incorporate the Buddhist symbol of the eight-spoked wheel, such as those of Menander I, as well as his possible grandson Menander II. On these coins, the wheel is associated with the Greek symbols of victory, either the palm of victory, or the victory wreath handed over by the goddess Nike. This symbology has led some to conclude that Menander adopted the Buddhist mantle of a "Chakravartin" during his lifetime; lit., "one for whom the wheel of law turns," translated as "King of the Wheel" in Western texts.
The ubiquitous symbol of the elephant may or may not have been associated with Buddhism. On some coin series of Antialcidas, the elephant holds the same relationship to Zeus and Nike as the Buddhist wheel on the coin of Menander II, tending to suggest a common meaning for both symbols. Some of the earlier coins of king Apollodotus I directly associate the elephant with Buddhist symbolism, such as the stupa hill surmounted by a star, also seen, for example on the coins of the Mauryan Empire or those of the later Kuninda kingdom. Conversely, the bull is probably associated with Shiva, and often described in an erectile state as on the coins of Apollodotus I.
Also, after the reign of Menander I, several Indo-Greek rulers, such as Agathokleia, Amyntas, Nicias, Peukolaos, Hermaeus, Hippostratos, Menander II and Philoxenus depicted themselves or their Greek deities forming with the right hand a benediction gestureMentioned in Bopearachchi identical to the Buddhist vitarka mudra (thumb and index joined together, with other fingers extended), which in Buddhism signifies the transmission of the Buddha's teaching.
At precisely the same time, right after the death of Menander, several Indo-Greek rulers also started to adopt on their coins the Pali title of "Dharmikasa", meaning "follower of the Dharma" (the title of the great Indian Buddhist king Ashoka was Dharmaraja "King of the Dharma")."Crossroads of Asia", p12. Also in "Taxila", by John Marshall: "By this time, both the title (Dharmikasa) and the symbol (the Dharmachakra) were indissolubly associated with Buddhism and their use was quite enough to proclaim the king's adherence to that religion", p33 This usage was adopted by Strato I, Zoilos I, Heliokles II, Theophilos, Peukolaos, Menander II and Archebios.
Altogether, the conversion of Menander I to Buddhism suggested by the Milinda Panha seems to have triggered the use of Buddhist symbolism in one form or another on the coinage of close to half of the kings who succeeded him. Especially, all the kings after Menander who are recorded to have ruled in Gandhara (apart from the little-known Demetrius III) display Buddhist symbolism in one form or another. On the contrary, none of the kings whose rule was limited to Punjab did display Buddhist signs, with the exception of the powerful Hippostratos, who probably took under his protection many Gandharan Greeks fleeing from the Indo-Scythians.Tarn
A 2nd century BCE relief from a Buddhist stupa in Bharhut, in eastern Madhya Pradesh (today at the Indian Museum in Calcutta), represents a foreign soldier with the curly hair of a Greek and the royal headband with flowing ends of a Greek king. In his left hand, he holds a branch of ivy, symbol of Dionysos. Also parts of his dress, with rows of geometrical folds, are characteristically Hellenistic in style. On his sword appears the Buddhist symbol of the three jewels, or Triratana.
One frieze of Sanchi, dated to the 2nd century BCE during the Satavahana period, also shows devotees in Greek attire and activities. The men are depicted with short curly hair, often held together with a headband of the type commonly seen on Greek coins. The clothing too is Greek, complete with tunics, capes and sandals. The musical instruments are also quite characteristic, such as the double flute called aulos. Also visible are carnyx-like horns. They are all celebrating at the entrance of the stupa. These men would probably be nearby Indo-Greeks."A guide to Sanchi" John Marshall. These "Greek-looking foreigners" are also described in Susan Huntington, "The art of ancient India", p. 100
Representation of the Buddha
The Indo-Greek may have initiated anthropomorphic representations of the Buddha in statuary, possibly as soon as the 2nd-1st century BCE, according to Foucher and others. Stupa constructions of the time of Menander, such as the Butkara stupa, incorporated niches which were intended to place statue or friezes, an indication of early Buddhist descriptive art during the time of the Indo-Greeks."They (the niches) were intended to hold a figured panel, relief-work, or something of the kind" Domenico Facenna, "Butkara I" Also Chinese murals are known which describe Emperor Wu of Han worshipping Buddha statues brought from Central Asia in 120 BCE.
Foucher especially considered Hellenistic free-standing Buddhas as "the most beautiful, and probably the most ancient of the Buddhas", assigning them to the 2nd to 1st century BCE during the reign of Menander, and making them the starting point of the anthropomorphic representations of the Buddha:
The willingness of ancient Greeks to represent and worship local deities is also attested in Egypt with the creation of the god Serapis in Hellenistic style, an adaptation of the Egyptian god Apis, or in Phrygia with the Hellenistic representation of the heretofore aniconic Cybele. On the contrary, Indian Buddhist art was traditionally aniconic (the Buddha was only represented with symbols), and the Iranian tradition (represented by the 1st century Indo-Parthians) also did not represent their deities in human form."Contrary to Iran, the Greco-Bactrian cults often employ representations of their deities". An Indo-Chinese tradition also explains that Nagasena, also known as Menander's Buddhist teacher, created in 43 BCE in the city of Pataliputra a statue of the Buddha, which is believed to be the Emerald Buddha, that is currently housed in Thailand.