About halfway through the movie (just before the intermission), the captain hosts a party, which he uses to some extent as a political statement by displaying a large Austrian flag. Later, he makes nationalistic comments in a conversation with an unnamed baron and Herr Zeller:
Baron: Is there a more beautiful expression of what is good in this country of ours than the innocent voices of our children?Zeller: Oh, come now, Baron, would you have us believe that Austria alone holds the monopoly on virtue?Von Trapp: Uh, Herr Zeller, some of us prefer Austrian voices raised in song to ugly German threats.Zeller: The, uh, ostrich buries his head in the sand and sometimes in the flag. Perhaps those who would warn you that the Anschluss is coming - and it is coming, Captain - perhaps they would get further with you by setting their words to music.Von Trapp: If the Nazis take over Austria, I have no doubt, Herr Zeller, that you will be the entire trumpet section.Zeller: You flatter me, Captain.Von Trapp: Oh, how clumsy of me; I meant to accuse you.
Near the end of the movie, when he gets a commission from the German navy, he says that "to refuse them would be fatal for all of us, and joining them would be unthinkable," and he decides to go into exile instead of betraying his country. Clearly, he loves Austria.
During the party, while the children are watching the partygoers from outside, one of them asks Maria about the dance they're doing. She replies, "It's the Ländler; it's an Austrian folk dance," and at Kurt's request, she starts dancing it with him. Soon, the captain arrives and takes his place. It seems that as the captain and Maria dance, their affection for each other grows, to the point that Maria becomes embarrassed and blushes.
Maria's knowledge of this folk dance demonstrates that she values Austrian culture, and at this moment, Austria and its national identity rank highly among the captain's concerns. While there are other of Maria's qualities that the captain admires, this one holds special importance here.
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