(@GWG: The advantage of numbers becomes less when mountain passes are involved, though. The best way for smaller forces to defeat larger ones is usually to hold them off at strategic chokepoints, such as mountain passes, where the larger force can only fight with a small fraction of their army at once. Again, not insurmountable, but it's a basic rule of military strategy, so the greatest resistance should probably expected both there and at the walls of the castle itself.)
((True enough, but the mountains around Arendell don't look completely impassable. Aside from the North Mountain, they look more like the Appalachians than the Rockies--and the North Mountain and the like are basically spires of rock, which doesn't make for ideal lines to hold. When attacked from all sides, they'll either need to spread themselves thin or leave holes--especially since the mountains don't look to be too fortified.))
(Anyone want to speculate about Olaf? GWG probably shouldn't reveal it until it becomes relevant, but you've kind of got to wonder where he is in all this. I bet he doesn't know what war is, and no one has the heart to tell him.)
((Same place Anna is: In the capital, probably aware of the war but not bloody likely to participate in it.
He might show up, but only because I find him
really annoying and want some catharsis.))
Maybe she upgraded Marshmallow to be a more effective personal bodyguard.)
((I've heard that Marshmallow was seen post-credits with Elsa's tiara, but I've only ever seen Frozen when other people were streaming it in my dorm's lobby so I didn't have the ability to check. Regardless, he's almost definitely stuck on the North Mountain, and probably wouldn't be retrieved, what with being symbolic of a few days Elsa really wants to get past. Not to mention that Marshmallow would present a terrible image.
Now, the general idea? Maybe.))