The Question: Can a Combination of Ming's Collapse and the Imjin War be Reasonably Said to Have Started an Asian Dark Age?
Context: I am trying to understand why, when Europeans contacted Japan, Korea and China in the 16th century East Asia had military superiority but by the 1850s, all three East Asian countries had gotten weaker than they had been 300 years before.
I'm basing this idea on 19th century Korean scholars, who say that Korea's "Closed Country Policy" was implemented on the logic that Japan had proven itself barbaric in the Imjin War and that the fall of Ming to the Manchus meant China was also barbarian - hence Korea had to protect the last sliver of civilization in the entire world. The Japanese seem to have done something similar in the early-mid Tokugawa. China I'm least certain on, but the stuff going on with Cixi seems to indicate a similar withdrawal into ultra-conservatism and isolationism.
For this hypothesis to be true, the war needed to have caused the three countries to cut off ties not just with the west, but with each other, and not repair relations for the next 200+ years.
Neither is true. Korea remained closely tied with China (why wouldn't they, China saved their ass, also Manchus defeated and forced Korea's submission). Japan repaired relationship and resumed regular diplomatic and commercial merely a couple of decades after the war ended. Japan and China did not cut off ties with the west either, they simply limited its point of entry.
I am trying to understand why, when Europeans contacted Japan, Korea and China in the 16th century East Asia had military superiority but by the 1850s, all three East Asian countries had gotten weaker than they had been 300 years before.
All three countries only had numerical superiority in the 16th century, as it was not yet possible (both technologically and politically) to ship large expedition forces half way around the world. When Europeans arrived in East Asia, they were already superior in naval and gunpowder technology. What the 16th century contact allowed was for Japan and China to catch up, but a lack of external pressure between the 17th and 18th century meant they didn't keep up.