In 1932, he went into exile in China to join the Korean Provisional Government (KPG) in their resistance against the Japanese occupation of Korea. In February 1934, he attended a joint KPG–KMT training course for resistance fighters at Luoyang that was jointly run by the KPG and the Chinese Kuomintang (KMT).
Two of the Korean instructors of the course, Chi Ch'ŏngch'ŏn and Kim Ku, frequently clashed over authority and funding for the class. Students were also ideologically divided, and factions that supported either Ji and Kim emerged. While Kim was nominally on Kim Gu's side, he and several other students, including Yeom Dong-jin, switched over to Ji's faction after a scandal. Kim and Yeom then joined the Ji-aligned New Korea Independence Party.[c]
After escaping the KNRP training camp, he went to Shanghai.
In January 1936, Kim, Oh Myeon-jik [ko], and many other Kim Gu-aligned alumni of the academy founded a militant independence organization called the Vigorous Blood Group.[d] Some members were anarchists, although Kim and some other members were right-leaning.
Kim and several others planned to assassinate the Japanese consul general in Shanghai, but were arrested by Japanese military police on 6 March 1936. Kim Hyeok was returned to Korea, and in April 1937, sentenced to three years in prison by the Haeju district court. According to a contemporary newspaper article, he expressed regret for having trained as an independence fighter while in prison. He was released on parole on 26 September 1939.
After his release, he likely returned to China. He remained there until the Liberation of Korea. Shortly afterwards, he departed from Beijing on 27 September and arrived in Korea on 10 October 1945. Afterwards, it is unclear if Kim participated in any of the various groups that other former independence activists joined. However, it is known that in mid-October 1945 he posted an advertisement seeking to reconnect with his former classmates from Luoyang, and successfully reconnected with several Kim Gu supporters.
Kim then became involved with a special task force in the Gyeonggi Province Police Department. Around late October 1945, the unit decided to assassinate 10 Japanese policemen. Kim Hyeok was involved in the 2 November assassination of Inspector Saiga Shichirō.[e]