By Matthew Parish
The Schleswig-Holstein Question was a notoriously problematic territorial dispute in the nineteenth century. It involved two groups of people, each with ethnic associations with neighbours (Denmark and Germany), living in adjacent pieces of land – Schleswig (Danish) and Holstein (German). For complex historical reasons, The Duchies of Schleswig-Holstein were treated as a separate state from either Denmark or Germany. This state had its own government; but the people of Schleswig and the people of Holstein had different ideas about how their government would change or its constitution would evolve.
Every time such a change occurred, it caused a war. That was because any change (whether enacting a new constitution or a change of Duke in accordance with competing hereditary principles applicable in each part of the territory) would be perceived as either pro-Danish or as pro-German; and the other side would declare war with a view to restoring the status quo ante.