User blog comment:IamJakuhoRaikoben/Chapter 454: Flying Dragon Squad and Osprey Squad, Review./@comment-5006572-20150928181922/@comment-7418318-20150928200819

Due to geography, yes.

The sea is south of them, so would you expect the foes to come from the sea, where they would be detected much late, or expect them to fly over 3/4 of the entire country, past several big cities including the capitol?

50 airships aren't exactly easy to overlook, especially considering how they can't fly too high, due to being open-topped. Go too high and your troops either suffocate or freeze.

So yes, it is actually surprising they came from the west and not from the south of Magnolia, barring short-cuts with teleportation, which they seem to have done.