The story takes place in 1918, but all of Vivien Leigh's fashions and hairstyles, as well as those of the other women in the cast, are strictly up-to-the minute 1937 modes.
With the sole exception of Conrad Veidt, all of the players speak perfect unaccented British English, regardless of their supposed nationality in the story, thus making their national sensibilities extremely confusing, especially in the case of Vivien Leigh, an alleged Frenchwoman, and, of course, except for Veidt, all the rest of the Germans.