Before the Korean War, on June 24, 1949, the YMCA Kwon Bup Bu held a Yun Moo Demonstration. Park Chul Hee demonstrated the "Jak Do Kwon", Park Ki Tae demonstrated "Bong Kwon" and Chung Do Kwan's Son Duk Sung, Uhm Woon Kyu and Lee Yong Woo demonstrated "Chan Jo." YMCA Kwon-bup-bu practice sessions started at 4:30 PM. In the beginning more than 500 members were recruited, but after three months, only 180 members were remaining because of the severity of the training. Yoon may have had some training in Chinese Quan-fa ("fist method"), which he taught under its Korean name of kwon-bop, but it is more likely that he taught the Japanese style of Shudokan karate. The reason for this possible deception is that many of the members of the Korean YMCA had been members of the independence movement during the occupation, and they certainly would have insisted that no foreign art be taught at the gym. On Mar. 5, 1947, a second club was opened at in the Ministry of Communications office, and taught by Nam-Suk Lee.
When Yoon was listed as missing during the Korean War and later declared legally dead, Nam-Suk Leegained control of the kwan. Yoon's surviving instructors built a central dojang in Seoul on Oct. 5, 1953, with Lee, Nam Suk elected as its second president and, from 1961 forward, he held several pivotal positions in the Korea Taekwondo Association, including vice president. Lee passed away in Southern California in late 2000.
The early Chang-moo-kwan black belts were: Lee, Nam Suk; Kim, Sun Gu; Hong, Jung Pyo; Park, Chul Hee; Park, Ki Tae; Kim, Ju Gap; Song, Suk Joo; Lee, Joo Ho; and Kim, Soon Bae.
The second Kwan Jang was Lee Nam Suk. The third Kwan, Jang Kim Soon Bae, had conflicts with Hong Jung Pyo and Park Chul Hee, which led to Hong and Park leaving the Chang Moo Kwan and opening their own school, the Kang Duk Won, in nearby Shinsuldong, Seoul, in 1956.