Connolly/Student's Guide, 5. The Orthodox Philosophical Systems

In the later epic period northern India was in a state of political and religious fragmentation. Across much of the north west, kingdoms ruled by the descendants of the Greeks who arrived with Alexander (called Yavanas, a term that came to refer to 'all the annoying outsiders of the western borderlands') denied the authority of the Vedas and were organized according to Greek-derived rather than bråhmanical codes. Moreover, heterodox traditions such as Buddhism and Jainism had also established a foothold in these areas. All this changed with the establishment of the Gupta Empire in 320 CE. Much as Constantine did with Christianity, the Gupta rulers gave brāhmans the job of creating ideological unity within their domain.