What would happen if the Duchy of Schleswig was never made into a fiefdom by the Danish Kings in early 12th century.
It would probably lessen some of the disputes that where in the area, both between the Danish kings and the Duke and his north germanic allies, and between Denmark and HRE in general, as the lack of the former alliances between the Duke and the other North Germanic counts/dukes, would mean that there were fewer claims around to get frisky for combat about.
In turn, (ignoring butterflies for now), this might lead to a (even) stronger Denmark doing the Kalmar union which might lead to Sweden either never trying to regain their Independence, or Denmark managing to suppress it, with equal amounts additional military and a stronger economy to make small concessions to individual nobles to keep them happy
It would probably lessen some of the disputes that where in the area, both between the Danish kings and the Duke and his north germanic allies, and between Denmark and HRE in general, as the lack of the former alliances between the Duke and the other North Germanic counts/dukes, would mean that there were fewer claims around to get frisky for combat about.
In turn, (ignoring butterflies for now), this might lead to a (even) stronger Denmark doing the Kalmar union which might lead to Sweden either never trying to regain their Independence, or Denmark managing to suppress it, with equal amounts additional military and a stronger economy to make small concessions to individual nobles to keep them happy