1) Greco-Buddhism and Birth of the First Buddha Image
Greco-Buddhism refers to the cultural syncretism between Hellenistic culture of Greek and Persian and Buddhism, which developed between the 4th century BCE and the 5th century CE in the area which that time was called Bactria and India. It was a cultural consequence of interactions begun by Greek invasion of India by Alexander the Great and carried further by the establishment of Indo-Greek rule and the hellenized empire of the Kushans. Which whole series of interaction end up in result of founding of Mahayana Buddhism.
There are many evidences and consequnces of interaction between Greek and Buddhist thought included the "Milinda Panha", a Buddhist discourse in the platonic style, held between king Menander and the Buddhist monk Nagasena. Buddhist tradition also recognizes Menander as one of the great benefactors of the faith, together with Asoka and Kanishka. Greek's influence also imprinted the concept of "Man-God" into Buddha's personality and deitified him as a god.
Greek influence also has been suggested the definition of the Bodhisattva ideal, between the 1st century BC and the 1st century AD, which redefine Buddhism around the universal Bodhisattva ideal, and its six central virtues of generosity, morality, patience, effort, meditation and, first and foremost, wisdom. These qualities are reminiscent the Greek Stoic philosophy. This marked the emergence of Mahayana doctrines of Buddhism, which may have begun around the 1st century BCE in northwestern India and Greek also carried this form of Buddhism that passed north and east along the Silk Road.
Later during the Hellenized Empire of Tocharian tribe of Kushan. Buddhism school which we now called them Mahayana start to officially included many of Zoroastrian, Greek, and Brahmanic deities into pantheon of Buddhism after long time of unofficial co-worshiping and religious syncretism, such as Indra, Zoroastrian's Zurvan and Brahmanic's Brahma as Buddhist version of Brahma, Persian's Mithras influence the creation of future Buddha and Savior Maitreya, Herakles as Vajrapani the Protector of Buddha, North wind Boreas, Tyche as the mother deity Hariti, etc. Concept of Persian's Paradise also influence cosmology of the "Pure Land" as well. And during reigned of Kanishka of Kushan, the Fourth Buddhist Council had convened and marked official birth of Mahayana Buddhism and this new syncretic form of Buddhism expanded fully into Eastern Asia soon after these events.
The most noticeable effect of Greco-Buddhism laid in art work which had center of creation is Gandhara which definitely Buddhist, while most motifs were of Western Asiatic or Hellenistic origin. But among all of art concept of Gandhara, the most important type of art work for most of nowadays schools is concept of anthropomorphic representation of the Buddha which now called "Buddha Image".
Before innovation of Buddha Image, Buddhist art was "aniconic": the Buddha was only represented through his symbols like an empty throne, the Bodhi tree, the Buddha's footprints, the prayer wheel. This according to one of the Buddha’s saying that discouraged representations of himself after the extinction of his body. But the Greek seem probably not feeling bound by these restrictions, and because of their cult of form, the Greeks were the first to attempt a sculptural representation of the Buddha by combining the image of a Greek God-King Apollo, the deified founder of the Indo-Greek Kingdom, Demetrius, with the traditional attributes of the Buddha.
Many of the stylistic elements in the representations of the Buddha, even in present days, point to Greek influence: the Greco-Roman toga-like wavy robe covering both shoulders, the contrapposto stance of the upright figures and the stylized Mediterranean curly hair and top-knot apparently derived from the style of the Belvedere Apollo, and the measured quality of the faces, all rendered with strong artistic realism of Greek art.
The Greek stylistic influence on the representation of the Buddha, through its idealistic realism, also permitted a very accessible, understandable and attractive visualization of the ultimate state of enlightenment described by Buddhism, allowing it reach a wider audience. During the following centuries, this anthropomorphic representation of the Buddha defined the canon of Buddhist art, but progressively evolved to incorporate more Indian and Asian elements.
The interaction of Greek and Buddhist cultures operated over several centuries until it ended in the 5th century AD with the invasions of the White Huns, and later the expansion of Islam, but its influences lived on to present day in Buddhism.