Karate is a martial art developed in the Ryukyu Kingdom prior to its 19th century annexation by Japan. It was brought to the Japanese mainland in the early 20th century during a time of cultural exchanges between the Japanese and the Ryukyuans. In 1922, the Japanese Ministry of Education invited Gichin Funakoshi to Tokyo to give a karate demonstration and, by 1924, Keio University established the first university karate club in Japan. In 1932, all major Japanese universities had karate clubs and in this era of escalating Japanese militarism, the name was changed from "Chinese hand" to "empty hand" - both of which are pronounced karate - to indicate that the Japanese wished to develop the combat form in Japanese style. After the Second World War, Okinawa became an important United States military site and karate became popular among servicemen stationed there. Later the martial arts movies of the 1960s and 1970s served to greatly increase its popularity and the word "karate" began to be used in a generic way to refer to all striking-based Oriental martial arts. Karate schools began appearing across the world, catering for those with casual interests as well as those seeking a deeper study of the art.