More than a million Koreans fled their homeland when the Japanese took over, T. R. Fehrenbach explains, in This Kind of War:
One refugee in the States, a Dr. Syngman Rhee, embarrassed the government. He had entered on an old Korean passport at the time of the takeover, and now in 1919 he requested a visa to visit the League of Nations, to make a protest over the treatment of his countrymen. Washington emphatically told him no, since he had no valid Japanese passport, and Washington did not want to offend its late ally, Japan. Generously, however, since Dr. Rhee had influential friends, he was allowed to remain in the United States.
In 1919, and later, the Japanese rulers of Chosun never quite dared expel the Western missionaries, probably not realizing in how little repute these emissaries were held in the Western capitals. For years the only contact the Korean people had with outside was through these missionaries. In Chosun, no anti-Western bias ever developed.
Koreans had learned the hard way that imperialism comes in many forms, and it can be black or brown or yellow, as well as white. Koreans would never afterward feel any sentimental racial cohesiveness with the rest of Asia. The Japanese occupation and policy of extirpation took care of that.