How does buddhism spread throughout asia

Buddhism spread across Asia through networks of overland and maritime routes between India, Southeast Asia, Central Asia, and China. The transmission of Buddhism to Central Asia and China corresponded with the development of the silk routes as channels for intercultural exchanges.

Explanation:

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first, the romans stayed isolated because they had to defend their own territories from neighboring cities that were harassing them, like the etruscans. second, once the romans managed to defeat their neighbors, and started to expand their territory, they started to build roads and bridges. finally, now that the romans have covered their territory with roads functioning as highways, they could mobilize their legions faster to assemble larger military units in a specific place.