At the end of World War II, several Kwans were set up. In the late 1950s, these Kwans united under the name Tae Soo Do. A few years later, the name Taekwondowas adopted for its similarity in name, to Taekkyon (practiced by the Goguryeo, Silla, Baekjae, and Goryeo Dynasties).

Lee Nam Suk's teacher Byung In Yoon had founded the "YMCA Kwon Bop Bu" (권법무) in 1946. Byung In Yoon had studied Chinese Kung Fu (ch'uan-fa) under the guidance of a Mongolian instructor in Manchuria.

Yoon trained karate at university karate club in Japan with Kanken Tōyama. When he trained Karate in Japan, Japanese karate students pursued the Korean student and beat them up. Yoon Byung-in angered by the Japanese karate students, Yoon Byung-in sprung into action using Chuan-fa. He deflected and evaded the karate students’ strikes and kicks to the point that they gave up and ran back to tell their teacher about what happened. 

Kanken Tōyama invited Yoon Byung-in to tell him about the non-karate martial art he used against his students. Yoon Byung-in explained to Toyama about his Chuan-fa education in Manchuria. Toyama appreciated the Chuan-fa background since he (Toyama) had studied Chuan-fa in Taiwan for 7 years, previously. They decided to exchange knowledge; Yoon Byung-in would teach Toyama Kanken Chuan-fa and Toyama Kanken would teach Yoon Byung-in his Shudo-Ryu karate.

Yoon later created his art and called as Kwon Bop Kong Soo Do. Unlike other taekwondo kwans, early Changmookwan was mainly based on Chinese Kung Fu (ch'uan-fa). The early Changmookwan taught Palgi kwon (which influenced by Bajiquan).

Yoon went missing during the Korean War. His teachings were carried on by his top student Lee Nam Suk, who changed the name of the school to Changmookwan.