The Changmoo-Kwan (Brighten Martial Arts School) and Kangduk Won (Academy Teaching Virtue) were two notable schools of Kong Soo Do established in South Korea following WWII. These schools had different chief instructors, but hailed from the same root school, the Kwon Beop Bu. The YMCA Kwon Beop Bu was established by Master Yoon Byung-in in Seoul, Korea in 1946. The unique aspect of the Jung Ang YMCA Kwon Beop Bu was the combination of a Shudokan karate and Chinese Chuan-fa curriculum. There are schools in the world still using the name Changmoo-Kwan or Kangduk Won and link themselves to the original curriculum. A quick glance at the background of the original Jung Ang YMCA Kwon Beop Bu curriculum and modem Taekwondo development can bring to light whether a school preserves the original Jung Ang YMCA Kwon Beop Bu instruction or is simply a modem Taekwondo school using the old "kwan" name.
Yoon Byung-in (May 18, 1920 – April 3, 1983).
The parents of Yoon Byung-in suffered under the Japanese occupation of Korea and fled to Manchuria. After diligent efforts to impress a Mongolian Chuan-fa master, the child Byung-In was permitted to study Chuan Fa or Gung Fu.
Yoon studied Chinese Chuan Fa under the guidance of a Mongolian instructor in Manchuria. Later, Yoon trained Karate at the Nihon University karate club in Japan with Kanken Tōyama. He was not initially engaged in karate training at the university, but was often seen practicing conditioning exercises against a courtyard tree. This tree reportedly started leaning from his practice. At one point, Japanese karate students pursued and started to beat up another Korean karate student who had skipped karate class to spend time with his sweetheart. After being persuaded by the other Korean student for help, Yoon used his Chuan Fa to skillfully deflect and evade the karate students’ strikes and kicks to the point that they gave up and ran back to tell their teacher what had happened. Teacher Tōyama invited Yoon to tell him about the skillful non-karate martial art he used against his students. Yoon 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 would teach Toyama Chuan Fa and Toyama would teach Yoon his Shudokan Karate. Yoon later created his art and called it Kwon Bop Kong Soo Do. Unlike other taekwondo kwans (schools), early Chang Moo Kwan was mainly based on Chinese Chuan-fa and Shudokan karate. The early Chang Moo Kwan taught the forms, Dan Kwon (단권, short fist), Chang Kwon (장권, Long Fist), Tai Jo Kwon (태조권, Fist of the Founding King), Pal Gi Kwon (팔기권, Eighth Manchurian Cavalry), and Doju San (토조산, Escaping Mist). In addition, they practiced a staff form developed by Yoon Byung-in and a staff form developed by Yoon Byung-in's friend and Jidokwan founder, Yoon Kwe-byung.
From 1951 to 1966, the whereabouts and activities of Yoon are unknown, as he traveled to North Korea in August 1950 with his older brother, Yoon Byung-du, a Captain in the North Korean Army.
In 1966 and 1967, he taught 'Gyuck Sul(격술, special combat strategy)' to North Korean special forces of the Moranbong. In late 1967, Master Yoon completed his assignment and returned to his supervisor position at a concrete factory in Chongjin, where he worked until his death from lung cancer in April 1983.
Grandmaster Chul Hee Park (1933 - 2016) began training with Byung In Yoon in Korea in 1946. After Mr. Yoon disappeared during the Korean War, Mr. Park continued to teach Kwon Bup along with Jung Pyo Hong. About 1954, Mr. Park and Mr. Hong founded a new Kwan, which Mr. Park named Kang Duk Won (School of Virtue). Mr. Park continued to teach Kang Duk Won Kwon Bup even in his final years. In November 2015 Great Grandmaster Chul Hee Park officially retired as world head of Kang Duk Won and passed the mantle of authority to his student Hwa Chong. His funeral on April 4th 2016 attracted many of Taekwondo's great luminaries, including his successor.