The conflict started over who would administer the Schleswig-Holstein region, which Prussia and Austria had annexed from Denmark in 1864. Prussia protested at the Austrian attempt to carve out duchies, and Austria started to mobilise in response. When the last diplomatic efforts failed at the Diet (the German Confederation parliament) in early June, Austria demanded mobilization of the member states (except for Prussia) and the Confederation dissolved, with the individual states started to choose sides. Meanwhile, Otto Von Bismark, the Prussian Minister President, had forged an alliance with recently unified Italy, who saw it as an opportunity to recapture more territory from Austria, including Lombardy and Venicia.
The lines between the pro and anti-Prussian states divided the Confederation in half, both physically and politically.
