Partitioned-off duke

The background for this phenomenon was the Treaty of Ribe of 1460, in which King Christian I of Denmark, after his election as Duke of Schleswig and Count of Holstein, had laid down that Schleswig and Holstein should forever be ruled by a joint sovereign, in a personal union with Denmark.

The promise was broken in 1544, when King Christian III of Denmark divided the territories between himself and his half-brothers John II the Elder and Adolf.

John II was given the title and rank of a duke, as well as the income from his own lands, but de facto rule over Schleswig and Holstein remained with his brother and uncle.

His partitioned-off duchy was not allowed to mint coins, nor to maintain a standing army.

After his death, it was further subdivided among his children, creating several collateral branches of the House of Schleswig-Holstein-Sonderburg.