Judo is the Japanese martial art with the longest history in the United States. During the 1890s, Kano Jiguro traveled to the United States and Europe to introduce and teach judo. In 1904 his student, Yamashita Yoshiaki, taught judo to Theodore Roosevelt and military cadets at West Point. Judo clubs soon sprouted across the United States; by the 1930s three California colleges were teaching it. Judo began to develop on a national level in the 1950s, when American servicemen, who had studied it while stationed in Japan, began returning home. It became a required course at the Air Force Academy in the early 1950s. National judo tournaments have been held since the Amateur Athletic Union made it an officially recognized sport in the 1950s. Americans have won 11 medals since the 1964 games when it made its first appearance as an Olympic sport. Karate and aikido also became popular when American servicemen returned from Japan in the 1950s. Tsutomi Oshima was the first Japanese instructor to teach karate in the United States. He established the first American dojo in Los Angles in 1956. He took a group of his American students on an exhibition tour of Japan in 1957, where they reportedly impressed Japanese karate masters with their skill.