As Dirty Dog stated, HWANG Kee's Moo Duk Kwan was the Kwan that refused the merger. However, a large portion of the Moo Duk Kwan supported the unification, and thus created the first of many splinters of the Moo Duk Kwan: Moo Duk Kwan Taekwondo vs. Moo Duk Kwan Tang Soo Do. Later HWANG Kee renamed his art Moo Duk Kwan Soo Bahk Do.
Actually I believe GM HWANG Kee started calling his art Soobahkdo in 1960 or so.
Here is a section from the Modern History that describes the Soobahkdo Hwe:
*
Chapter 2, Section 5: HWANG Kee and the Korea Soo Bahk Do Association
As the 1959 Korea Taekwondo Association was collapsing in April 1960, HWANG Kee took advantage of the
disruption and chaos during this period. When the huge demonstrations against ROK President RHEE Syng
Man's corruption broke out, HWANG Kee used a powerful man in politics to finish registering the Korea Soo
Bahk Do Association with the Korea Amateur Sports Association at the Ministry of Education.
The members of the 1959 Korea Taekwondo Association were upset and petitioned the Ministry of Education to protest what they considered a wrong doing. At the time, every representative from each Kwan said HWANG Kee's unilateral behavior was a misdeed.
The following is part of the 1959 Korea Taekwondo Association petition against the Korea Soo Bahk Do Association:
"We, the Korea Taekwondo Association, cooperate with the national rebuilding committee's policies, but we must petition the registration of the gangster's (gangpae) hotbed, the Korea Soo Bahk Do Association (Tang Soo Do Moo Duk Kwan). Soo Bahk Do's official discipline is to train both body and spirit, but in reality, it is just an unsportsmanlike school.
The evidence is as follows:
1. In Kwang Ju, Soo Bahk Do trainees beat up students of Kwang Ju High School and gave rise to public criticism, so much so the Ministry of Education stopped Tang Soo Do training;
2. In Taejon, Soo Bahk Do trainees fought with another gangster group in the street;
3. The high ranking leaders of a Soo Bahk Do school beat up the workers of the Taejon Theater when they were not given free tickets;
4. One military soldier was stabbed and injured by a Soo Bahk Do trainee and now the trainee is in jail.
. . .
This kind of behavior is happening all over the country. There are numerous other incidents of misconduct we cannot mention. Furthermore, Dan certificates were given recklessly, with the Soo Bahk Do Association charging a large amount of money for the certificates to fulfill their desire and greed, which in effect, amounted to the selling of rank. Using these bought certificates, Soo Bahk Do trainees quietly threatened people and
bilked restaurants by refusing to pay their checks. . . . Soo Bahk Do caused a big social disruption and was once banned by the Ministry of Education. So how can the Soo Bahk Do Association be officially registered as a legal (sa dan bup in) Association? As a matter of course, the registration must be stopped and the Association must be eliminated.
Korea Taekwondo Association
June 1960"
After the 1959 Korea Taekwondo Association petitioned the Ministry of Education and the Korea Amateur Sports Association, it requested sanctions against the Korea Soo Bahk Do Association, but the Ministry of Education said it could not stop the freedom of the Association. However, the Ministry of Education requested the registration of a new Association because it couldn't recognize two different Associations in one sport. In the
meantime, General PARK Chung Hee carried out a coup de tat on March 16, 1961.