Modern history of East Asian martial arts
Taekwondo was developed from karate for use in the Republic of Korea Armed Forces from 1954. For this purpose, karate terminology needed to be "nationalized". The name "taekwondo" is due to shotokan practitioner and army general Choi Hong Hi. After the Korean War, Taekwondo was further developed into a purely sportive discipline, since 1973 overseen by the World Taekwondo Federation. 
During 1964-1966, Choi Hong Hi continued to promote taekwondo, working to put together a world-class exhibition team. Taekwondo's emphasis on jumping and flying kicks dates to this period. While taekwondo was based off karate, the structural changes made in the 1950s and 1960s were significant, and it cannot now be considered a branch of karate, but is a standalone modern martial art. Taekwondo was presented at the Summer Olympics as a demonstration sport in 1988 and 1992, and became an official Olympic discipline in 2000.
Shūdōkan
Of the nine schools, or Kwan's (Kan) that merged to form Taekwondo, four of those schools have lineages that trace back to Toyama Sensei through three Korean men who trained in Japan while Korea was under Japanese occupation. These three men were Kim Ki Whang, Dr. Yoon Kwey Byung and Yoon Byung In. Dr. Yoon and Yoon both trained with Toyama Sensei and are both listed in his student role books as ""Shihan"." Both these men taught a mixture of Toyama Sensei's methods along with the Chuan Fa they learned in Manchuria, before the Taekwondo unification movement. At that time, they founded Tang Soo Do or Kong Soo Do schools in Korea. The first Kwan (Kan) where they worked as teachers was the Yunmookwan (later: Jidokwan). Kim Ki Whang received his 3rd dan from Toyama Sensei and had moved to the United States in the early 1960s to teach Taekwondo. Later, the Chang Moo Kwan, Han Moo Kwan and Kang Duk Won branched off from the first Kwan. This is according to Han Moo Kwan founder Kyo Yoon Lee as written in his book Global Taekwondo 2009, and, A Modern History of Taekwondo, by Won Sik Kang and Kyong Myung Lee (1999).