In 1933, joined anti-Japanese forces in Manchuria and began a long association with Kim Il Sung.

O Jin-u is held responsible for the Korean axe murder incident and Rangoon bombing as head of the KPA.

According to the testimony of film director Shin Sang-ok, who was abducted from North Korea, "O Jin-u once said that if he was drunk, he would wipe out Busan in a week if the general commanded him.

Lunch in Daejeon, dinner in Busan... " In January 2017, it was reported that his three sons, O Il-hun, O Il-jong and O Il-su had been "purged" by Kim Jong Un.

[3] No official reason was given for why they were purged; however, it is believed that Kim Jong Un viewed their relation to O as a possible threat to his rule of the DPRK.

[3] Considering how revered O was in the DPRK (still having the title of "Revolutionary Martyr"), the incident shocked observers, as respected officials' relatives tended to be well taken care of.

O Jin-u, who had been victorious in the North Korean regime, suffered a worsening case of lung cancer, and his frequency of public appearances decreased significantly during this time.