(Ref --Wikipedia)
The Indo-Greek Kingdom or Graeco-Indian Kingdom[1] was a Hellenistic kingdom covering various parts of the northwest regions of the Indian subcontinent during the last two centuries BC, and was ruled by more than 30 kings, often in conflict with each other.The kingdom was founded when the Graeco-Bactrian king Demetrius invaded India early in the 2nd century BC. Pushed by the Scythian tribes, the Graeco-Bactrians were forced to invade India. The Greeks in India were eventually divided from the Graeco-Bactrians centered in Bactria (now the border between Afghanistan and Uzbekistan). But, the Greeks failed to establish a united rule in north-western India. The most famous Indo-Greek ruler was Menander (Milinda). He had his capital at Sakala in Punjab, modern Pakistan, and he successfully invaded the Ganges-Yamuna doab.
The expression "Indo-Greek Kingdom" loosely describes a number of various dynastic polities, traditionally associated with a number of regional capitals like Taxila, (modern Punjab (Pakistan)), Pushkalavati and Sagala. Other potential centers are only hinted at; for instance, Ptolemy's Geographia and the nomenclature of later kings suggest that a certain Theophila in the south of the Indo-Greek sphere of influence may also have been a satrapal or royal seat at one time.
During the two centuries of their rule, the Indo-Greek kings combined the Greek and Indian languages and symbols, as seen on their coins, and blended ancient Greek, Hindu and Buddhist religious practices, as seen in the archaeological remains of their cities and in the indications of their support of Buddhism, pointing to a rich fusion of Indian and Hellenistic influences. The diffusion of Indo-Greek culture had consequences which are still felt today, particularly through the influence of Greco-Buddhist art.
The Indo-Greeks ultimately disappeared as a political entity around 10 AD following the invasions of the Indo-Scythians, although pockets of Greek populations probably remained for several centuries longer under the subsequent rule of the Indo-Parthians and Kushans.