Upvote:1
By supporting German states in their bid for independence from Denmark, Prussia was able to position itself as a champion of German nationalism, particularly in the question between a "small" Germany excluding Austria, and a "great" Germany including it.
Upvote:7
Schleswig-Holstein became the rallying point for a united Germany, first in a war of Prussia and Austria against Denmark for the two provinces, then in a war of Prussia versus Austria. When Prussia won both times, it established itself as the dominant power in north Germany, around which the north German states coalesced. (Pulling in south Germany came later, after the victorious Franco-Prussian war.)