Political map of Europe & the Mediterranean 24 December 1863 (Schleswig-Holstein Question): Schleswig and Holstein (Schleswig-Holstein Question) were two largely German duchies which had long been ruled by Denmark. In 1863 the Danes revised their constitution to tie Schleswig more closely to Denmark - outraging German nationalists (Pan-Germanism) across Europe, who wanted the two duchies free from foreign rule. Supporting the nationalist cause, the small German states of Hanover and Saxony marched into Holstein (Second Schleswig War).