Have you been able to come up with a list of all of Korea's crisis
wars from the 1500s to the present?
I've been doing some light research the past couple days, and its been very difficult to find crisis wars between the Imjin War and WWII for Korea.
Here's a brief analysis of Korea's history between the Imjin War and WWII.
1592-1598, The Imjin War: Japan devastates Korea in two brutal invasions, but due to heroic resistance both from Admiral Yi and guerilla armies and from the Chinese Empire, Japan is successfully repulsed, though Korea lies in ruins. evaluates to a crisis war for Korea
In 1627 and 1636-1637 the Manchus to the north launched two invasions of Korea that succeeded in ending their ties with the Ming Dynasty in China and transferring their allegiance to the Manchu Qing Dynasty. I evaluate both invasions to be mid-cycle wars as the Korean resistance to both invasions was not as strong as it was to the Japanese invasion, not due to lack of animosity but there definitely appears to be a lack of energy. Nevertheless, both wars are highly likely to have been crisis wars for the Manchus, and very harsh peace terms were forced upon the Koreans that left a severe psychological wound for decades to come.
Nevertheless, between 1637 and 1811 I have not been able to find any record of a crisis war, or even any war either external or internal for Korea. They did assist with a war against the Russians in the 1650s, but everything I can find about that war evaluates it as a non-crisis war, with the external influence of the Qing bringing the Koreans into the war, and it does not seem to have been a major war for either side.
There were political squabbles during the late 1600s and early 1700s, but nothing more severe than the execution of a few bureaucrats - hardly a crisis war.
From 1811-1812 there was a peasant uprising, but I've not collected enough sources to evaluate for sure that it is a crisis war, but it keeps being mentioned, so I can tentatively evaluate it as a crisis war.
There was another major uprising that involved 71 towns rebelling simultaneously from 1862-1863, but I cannot tell from what I've found if this was a crisis war or a mid-cycle war.
The Donghak uprising of 1894-1895 coincided with the Sino-Japanese War of 1894-1895 that was fought primarily in Korea. The two wars appear to evaluate to a crisis war, ending Korea's ties to China under the tributary system and compelling the Koreans to enact several reforms that began the modernization of the country.
In 1910 the Japanese annexed the country without armed resistance, in keeping with the end of a recovery era and the beginning of an awakening, but non-violent/low-level violent resistance seems to have begun immediately, with Japanese rule encompassing most of Korea's awakening - marked by cultural revival and substantial civil unrest, student uprisings/movements, and low-level/intermittent violence. A generational awakening climax appears to have occurred in 1929 with the mass student uprising in that year.
Korea was in an unraveling era when WWII began, and the war evaluates to a crisis war because of the intense suffering of the Korean people and the actions of the Japanese that amounted to an attempt to exterminate the Korean people.
*much of the source material of this research comes from Wikipedia, both the general Korean history section and skimming over the reigns of the Korean kings between 1600 and 1900.