What was the significance of the Schleswig-Holstein question in the 19th century?

Question

As the title states, what was the specific significance of the Schleswig-Holstein question (Denmark and Prussia arguing over contested lands bordering the two nations) as it directly relates to German unification in 1871 and the concept of German identity that existed throughout the 19th and 20th centuries?

Answer 1

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.)

Answer 2

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.