Pre-WW2, Kilsoo Haan repeatedly warned the United States about Japanese attacks and accurately supplied every conceivable detail: midget submarines as well as aircraft at Pearl Harbor, giant submarine aircraft carriers on the high seas that almost bombed San Diego with plague germs until Tojo cancelled the air strike, and a joint Chinese-Japanese attack - Operation Ichi-Go - against the American and Chinese Nationalist forces, which drove through Chiang Kai-shek's much larger army. When US political bungling helped to create a Communist North Korea, Haan continued to supply information about Soviet nuclear tests in Siberia, the development of Soviet guided missiles, and the North Korean invasion of the Republic of Korea, which led to thousands of American and British casualties. He was ignored. The story of American influence in Korea and dealings with Japan provides a little-known background to the Pacific War and remains a factor today in international politics.