how has south east asia historically functioned both as a shattered belt and a buffer zone

Answer 1

I would guess that it was both a powder keg and a haven because of European colonization that opened it up to the west, whether the countries wanted it or not.

Spain weighed anchor in the Philippines, Holland, Macao, England, Japan and China, and France, Indochina. Prosperity and resentment both grew exponentially with the domination of Europe in the region, which led to the Boxer Rebellion and the opium wars between China and England.. Southeast Asia wanted independence on one hand, but also a thriving economy, thus the dichotomous atmosphere in the region..