In the area of international relations, the research of the Imjin War has mainly focused on the bilateral relations exclusively among Korea, China, and Japan. In documents from that era, however, can be found many suggestions for a military cooperation including some Southeast Asian countries like Liukyu and Siam. The Jurchen, a rising power located between Ming and Chosun, volunteered to send a troop of thirty thousand men.
A close look at the discussions shows some interesting points. Some suggestions were very seriously discussed in Chosun as well as China, even though they could not, for some reasons, be realized. And the suggestions were strategically meaningful, because Japan should have kept some of its military forces in its territory and prepare for a possible attack from the third countries. The suggestions, however, were rejected by Ming and Chosun themselves, who might have needed an urgent help from other countries. They thought that the a military help might lead to change in power relations in East Asia.
The failure of a military cooperation with a third country reflected the non-function of the so called Chinese Empire, that governed East Asia at that time. The appearance of quite lively ideas on the cooperation, including East Asian countries, however, implies a gradual change of the traditional international system in East Asia.