The war left significant legacies in all three countries. In the context of Japanese imperialism, the invasions are seen as the first Japanese attempt to become a global power. The partial occupation of Korea developed the Japanese concept that Korea belonged within Japan's sphere of influence, and the Japanese leaders of the late 19th and the early 20th centuries used the 1592-1597 invasions to reinforce the justification for their 20th century annexation of Korea. In China, the war was used politically to inspire nationalistic resistance against Japanese imperialism during the 20th century. In Chinese academia, historians list the war as one of the Wanli Emperor's "Three Great Punitive Campaigns". Contemporary Chinese historians often use the campaigns as an example of the friendship the two nations shared. In Korea, the war is a historic foundation of Korean nationalism and, as in China, inspired and was used politically to instigate nationalistic resistance against Japanese imperialism during the 20th century. Korea gained several national heroes during the conflict, such as Admiral Yi Sun-sin. Even today, anti-Japanese sentiment in Korea can be traced as far back as the Japanese invasions in 1592, although the principal cause is rooted in more recent events, particularly the hardships suffered by Koreans during the Japanese occupation of Korea from 1910 through 1945.. How many years did Koreans suffer hardships during the Japanese occupation?