Jutland peninsula is made up of the German Bundesland of Schleswig-Holstein. Schleswig-Holstein has two parts: the former duchies of Schleswig (Danish fief) and Holstein (German fief), both of which have passed back and forth between Danish and German rulers several times. The last adjustment of the Danish–German border followed the Schleswig Plebiscites in 1920 and resulted in Denmark's regaining Northern Schleswig ( or more commonly today: "Sønderjylland"). The historical southern border of Jutland are areas south of Kiel, Husum and Rendsburg, but the river Eider was the border between the former duchies of Schleswig and Holstein, as well as the historical
Battle of Jutland illustrated the irrelevance of battleship fleets following the development of the submarine, mine and torpedo. In this view, the most important consequence of Jutland was the decision of the Germans to engage in unrestricted submarine warfare. Although large numbers of battleships were constructed in the decades between the wars, it has been argued that this outcome reflected the social dominance among naval decision-makers of battleship advocates who constrained technological choices to fit traditional paradigms of fleet action. Battleships played a relatively minor role in World War II, in which the submarine and aircraft carrier emerged as the dominant offensive weapons