When Austria brought the Schleswig-Holstein dispute before the German Diet on 1 June and also decided on 5 June to convene the Diet of Holstein on 11 June, Prussia declared that the Gastein Convention of 14 August 1865 had thereby been nullified and invaded Holstein on 9 June. When the German Diet responded by voting for a partial mobilization against Prussia on 14 June, Bismarck claimed that the German Confederation had ended. The Prussian Army invaded Hanover, Saxony and the Electorate of Hesse on 15 June. Italy declared war on Austria on 20 June.