The extras in the film mostly speak Cantonese - a Chinese dialect used mainly in southern China. If the film were to be more accurate, the extras would speak Mandarin, but most Chinese residents in the Los Angeles area (who worked as film extras) spoke Cantonese, necessitating Josef von Sternberg use Cantonese. Even so, Cantonese was spoken by a lot of Chinese as Mandarin gradually gained ground.
It was Josef von Sternberg's intention to have the style of the film reflect the rhythm of a train journey. This explains the film's tight pace and the rather staccato quality of the dialogue.
China initially banned the movie, demanding its withdrawal from worldwide circulation. The ban was lifted when Paramount pledged not to make another film involving Chinese politics.
(at around 40 mins) There is an obvious jump cut that deletes the details given by Major Lenard (Emile Chautard) as to the nature of his "disgrace" which instigated his removal from military service.
1,000 extras were used in the making of the film.