I’m not quite sure if you’re disregarding the fact that Norway and Denmark haven’t had a war for hundreds of years because they don’t share a land border? In any case i can point out that there were plenty of Norwegian-Danish hostilities before the union time. With both Norway and Denmark being big on seafaring, the waters between Norway and Denmark have historically been seen much more as a highway (as you say about the Anglo-Portuguese waters) than anything else.
The distance is shorter though, so I would rather compare the Norwegian-Danish border to the Anglo-French border, and the lack of a land border there hasn’t really prevented any wars.
I’m not quite sure if you’re disregarding the fact that Norway and Denmark haven’t had a war for hundreds of years because they don’t share a land border? In any case i can point out that there were plenty of Norwegian-Danish hostilities before the union time. With both Norway and Denmark being big on seafaring, the waters between Norway and Denmark have historically been seen much more as a highway (as you say about the Anglo-Portuguese waters) than anything else.
The distance is shorter though, so I would rather compare the Norwegian-Danish border to the Anglo-French border, and the lack of a land border there hasn’t really prevented any wars.
Norway occupied parts of Greenland for a while, 1931-1933, I’d call that an act of aggression against Denmark and thus a war even if it was ultimately resolved peacefully and the claim didn’t concern the Danish mainlands.