The nobles of Holstein had, however, gradually succeeded in extending German influence and the German language into Schleswig, so that this Duchy had become more than half German.

Schleswig and Holstein were also joined together by very old customs, which were, it is said, founded on charters given by the Kings of Denmark; it was claimed that the two Duchies were always to be ruled by the same man, and also that they were to be kept quite distinct from the Kingdom of Denmark.

These charters are not undisputed, but in this case, as so often happens in politics, the popular belief in the existence of a right was to be more important than the legal question whether the right really existed.
The trouble began about 1830.

There was a double question, the question of constitution and the question of inheritance.

The Danes, desirous to consolidate the Monarchy, had neglected the rights of the old local Estates in the Duchies; this led to an agitation and a conflict.