[6] He filed his doctoral dissertation at the University of Bremen in 1985, on the topic of Japanese Marxian economist Nobuo Okishio and the labour theory of value.
[6][2] He was influenced in this by a number of famous South Korean leftists in Germany, including Song Du-yul and Yun Isang; they later suggested that he could help his motherland by working as an economist in North Korea.
[4] His activism also attracted the attention of North Korean government representatives, who further attempted to entice him to defect, claiming that his wife could receive free treatment for her hepatitis in Pyongyang.
Instead of receiving the promised medical treatment, he and his wife were held at a military camp and forced to study the Juche ideology of Kim Il Sung, then employed making propaganda broadcasts to South Korea.
[3] It was reported that his family were alive as of September 2011, and had recently been relocated from Yodok prison camp to a restricted area in Pyongyang.
[9] Oh's fight to reunite his family gained wider media coverage with the 2011 establishment of the Daughter of Tongyeong Campaign, which aims to petition UN Secretary-General Ban Ki-moon to address the situation.