Did Japan invade Korea?

Japan invaded Kangwha Island and forced an “unequal treaty” on Korea in 1876 ceding monopoly trade and extraterritoriality rights to Japan. Japanese troops were garrisoned in Seoul by the Treaty of Chemulpo, in 1882, ostensibly to protect the legation after the Imo incident.

Japan invaded South Korea again, in force, during the Sino-Japanese war in 1894 and effectively didn't leave until their defeat in August 1945 when they surrendered to the US in WWII. The 1894 invasion included the occupation of Seoul and taking the Korean "emperor" captive. The Japanese invaded the Korean island of Euleongdo in 1895 during the Sino Japanese war. They took over the police force there. Then the Japanese without notice in January 1905, "transferred" the "stateless" nearby island of Dokdo to itself. In 1895 Japanese assassins invaded the Korean royal palace and assassinated Queen Myeongseong who was opposed to their overbearing military and diplomatic presence and their continuing efforts to dominate Korean affairs.

(Source- JTBC News 8.6) Kishi Nobusuke, South Korea- Japan Cooperation Committee President (1963): "No person here thinks of this as a war of invasion." This is the revisionist mythology of Shoin school imperialists and advocates of the Greater East Asian Co-Prosperity Sphere. Kishi an accused class A war criminal, was propelled to the position of prime minister in post war Japan by the US. He was Abe's maternal grandfather and patron.

Japan was thereafter the predominant military power with interests in Korea and was only held in check by the diplomatic presence of Russia and the US, the only two military powers at the time who would conceivably oppose the Japanese. The Russians were defeated in the Russo-Japanese War, in 1904. The war was a contest to control Korea and areas of northeast China. The US had given its blessing to Japanese political and military dominance of Korea in the Taft-Katsura agreement and that was later formalized in the Treaty of Portsmouth. The infamous Ulsan Treaty of 1905 was then forced upon Korea, through a combination of threats and bribes by the Japanese legation, which they were fully capable of enforcing. At that point the Japanese took the Korean crown prince hostage and installed an even larger military garrison in Seoul. The annexation of Korea in 1910 merely formalized a process that began with the late 19th Century invasions, and culminated in effective political control in 1905. The entire period was characterized by the Japanese use of military force, intrigue, and political oppression to achieve their goals. According to a record left by Ahn Jung-geun, the Korean patriot who assassinated Ito Hirobumi, the Japanese leader he believed most responsible for the reduction of Korea to a colonial vassal status, the Japanese imposed 14 unequal treaties on Korea before it was annexed. Before the formal annexation a vicious exploitation of Korean resources, expropriation of property, and exploitation of its people by the Japanese was well underway.

Japanese revisionist history declares their occupation and annexation of Korea, not as an invasion and oppressive occupation, but "beneficial to Korea." The colonization was entirely illegal, accomplished by military invasion, characterized by exploitation of the people and resources of Korea, and enforced by torture and summary executions.