Japanese occupation changed North Korea, with various citizens either collaborating with or actively resisting it. One of those resistors was a guerrilla fighter named Kim Song Ju, who would later be known as Kim Il Sung. If you believe North Korean propaganda (which you shouldn’t) Kim Il Sung was born of humble farmers and formed a secret Korean resistance during the occupation. In fact, his grandfather was a Protestant minister, he spent most of his youth in China, and the units he fought with were organized either by the Chinese or Russians.