Ah, civilization discussion. Even though it is deviating from the topic (JF-17) I would like jump in. I have read little bit about this topic though my knowledge is that of a layman on this subject and may be riddled with discrepancies. Nevertheless, here are my two cents. You are more or less correct. But even with the Persian barrier between Greeco-Bactria and Greece+Macedonia, the people in Greeco-Bactria continued to maintain many of their Greek culture, language, and other heritage aspects. They maintained their identity for quite a significant time, even after their fall as ruling elites. But the resurgent Persians to the West and emerging Indian origin kingdoms to the East were neither able to wipe the Greeco-Bactrian culture and language out nor were they able to dislodge Greeco-Bactrian nation. They were replaced by Indo-Greeks, who too maintained Greek culture and language for a significant time period as evinced by the coins of that era. Even when Indo-Scythians and later Parthian Empire (both Persians) took over Greek language and culture remained quite prevalent in South-Central Asia. The major change in Greeco-Bactrians and Indo-Greeks was perhaps of religion as in later periods they began converting to Buddhism. Menander-I Soter (Indo-Greek king) converted to Buddhism and occupied much of what is now modern day Pakistan. Thus, in a way he is the ancient founding father of Pakistan as he left quite a mark on the ancient history of this land.
