Answer: British Censorship

In 1963, the British authorities overseeing the then-British-territory of Hong Kong passed a law requiring that all movies produced by the Hong Kong movie industry feature English subtitles.

The decision wasn’t intended to make the movies accessible to English speakers, but to instead make it easy for British censors to monitor the content of movies without additional study of foreign languages.

While censorship and political monitoring was the intended purpose, the much farther reaching unintended result was that thousands of Hong Kong cinema films were now accessible to Western viewers. Martial arts and action films proved particularly popular and the effects of widespread consumption of those films can be seen in the rise of English-language martial arts films of the late 20th century and the history of movie combat choreography.