Jilin Province is located in Northeast China, in Manchuria, and shares a border with north Korea. Jilin is important in the history of the Korean struggle for several reasons. It's the place where Kim Il-sung joined the resistance movement, and also where, as a teenager, he founded the Down-With-Imperialism Union, which contemporary literature in north Korea considers as the original foundations of the Workers' Party of Korea (WPK). A large number of Koreans had fled to Jilin to escape the brutal Japanese colonial occupation of Korea, and Jilin was home to the largest base of Korean resistance.

In the struggle against Japanese imperialism, Korean and Chinese communists (and at various points, nationalists) were part of a united front. In fact, at the urging of the Third International (Comintern), which at the time was organizing the world communist movement, Korean communists joined the Chinese Communist Party. It's estimated that, when the merging process was consolidated in 1931, as much as 90 percent of the Chinese Communist Party was actually Korean, as their efforts at recruitment among the peasants in the region had been much more successful.

-- Foreword to Socialist Education in Korea by Kim Il-Sung, written by Derek R. Ford and Curry Malott, emphasis mine.