Does the Major Know? (Possible Spoilers)
There's really two parts to this question. One is: Does he figure out "Suzu" is a woman early on, in the train? My opinion is, he doesn't, although I can see why some men would find it hard to believe since he holds her in his arms during the thunderstorm. Since the idea of holding Ginger Rogers in my arms is pretty, uh, exciting to me, I have a hard time myself with believing he can't tell right then. However, since later scenes such as the "moths around the light" speech aren't as much fun if the Major knows who he's really talking to, I'm going to have to go with the conceit of the Major's obliviousness and say he hasn't figured it out yet.*
The second part to this question is, does the Major know that "Suzu" is a woman when he goes to the family house in Iowa at the end? On this one, I think the answer is yes. That little smile he gives at the train station after he exclaims "Suzu!" is the giveaway for me, but there are other clues if you watch carefully in the scene with "Suzu's Mom".
Anyway, I'd love to hear what others who have watched this movie think about this question.
*Does anyone else notice, as I have lately, that a surprising amount of movies made in the 30s and 40s portray the women as actually smarter than the men?