Nam Tae Hi made a big contribution to the Oh Do Kwan. After ROK President Rhee Syng Man sponsored General Choi, the Oh Do Kwan grew rapidly. Choi wanted to teach Tang Soo Do to everyone in the military. After the Vietnam War broke out in the early 1960's, General Choi began sending military Taekwondo instructors to Vietnam in December 1962.
Oh Do Kwan only approved Chung Do Kwan dan ranks, so dan ranks from other kwans were not approved; they were called "Civilian Dan rank." New recruits with Taekwondo dan rank from other kwans had to pass a test to receive dan rank in the military. This caused complications between the Oh Do Kwan and other kwans, led to discrimination against civilian dojangs, and spread the Oh Do Kwan's reputation. After Choi Hong Hi founded the International Taekwondo Federation, he deviated from the KTA, which weakened the Oh Do Kwan.