I would like to hear a clarification of your claims, this is the first time I hear this.
The only wars that could fit this picture I remember are the Prussian-Danish Wars over Schleesvik-Holstein during the unification of Germany, and the Second World War. The border was afterwards fixed according to population majority of each area.
Oh, my goodness ~ the wars ~ Denmark has had an almost endless succession of wars going as far back in history as Runic Characters exist. One of the larger ones ~ the Thirty Years War ~ had what is called the "Danish Phase" ~ only 5 years long.
Like I said just one thing after the other.