Prussia and Austria agreed to share sovereignty over Schleswig and Holstein but divided day-to-day administration: Prussia ran Schleswig and Austria ran Holstein. The deal eased tension after the 1864 war with Denmark, but it also created constant disputes over how the duchies should be governed. Those disputes became a main trigger for the 1866 war.
Austria brought the Schleswig-Holstein conflict to the Federal Diet (the German Confederation’s central assembly), seeking a confederation-level decision on Holstein. Prussia argued this move violated the Gastein Convention and treated it as a hostile step. The quarrel pushed both powers toward open confrontation.
Prussian forces moved into Holstein, the duchy Austria was administering, claiming Austria had broken earlier agreements. Austria protested and looked to the German Confederation for support. The action made war between the two German great powers difficult to avoid.
The Federal Diet voted for mobilization of non-Prussian federal troops, a step aimed at forcing Prussia to back down. Prussia rejected the vote as illegitimate and treated it as a declaration of “federal execution” (collective enforcement) against Prussia. This decision is commonly marked as the formal outbreak of the Austro-Prussian War.
Italy joined Prussia as a co-belligerent against Austria, aiming to annex Venetia and advance Italian unification. This opened a second major front, forcing Austria to divide attention between Germany/Bohemia and northern Italy. The wider conflict is often called the Seven Weeks’ War because the main campaign moved quickly.
Austrian forces beat the Italian army at Custoza in Venetia. The defeat disrupted Italian operations and temporarily reduced pressure on Austria’s southern front. Even so, Italy remained in the war, and its claims would still shape the peace settlement.
The Kingdom of Hanover won a battle against Prussian troops at Langensalza. However, Hanover was soon surrounded by larger Prussian forces and could not link up with allies. The episode showed how fast Prussia could concentrate forces and remove opponents in northern Germany.
At Königgrätz (also called Sadowa) in Bohemia, Prussia defeated Austria and its allies in the war’s decisive land battle. The victory demonstrated Prussia’s operational planning and helped end Austria’s leading role in German affairs. After this defeat, Austria sought an armistice and peace terms.
Prussian troops defeated Bavarian forces at Kissingen during the western “Main campaign.” These battles pressured Austria’s German allies and helped Prussia control key areas before negotiations. The fighting also signaled that the old German Confederation could not coordinate an effective defense.
After Königgrätz, Prussia and Austria signed preliminary peace terms at Nikolsburg. The document set the direction for a final settlement: Austria would give up influence in Germany while avoiding a harsh occupation or extreme penalties. It prepared the way for the definitive Treaty (Peace) of Prague.
Austria and Italy agreed to an armistice at Cormons, stopping major military operations on the Italian front. This armistice set up the formal peace settlement that followed in October. It also reflected how the wider war’s outcome in central Europe shaped what happened in Italy.
Prussia and many northern and central German states signed an alliance treaty (often called the August Alliance). It placed their armed forces under Prussian leadership and committed them to negotiate a new federal structure. This created a practical replacement for the collapsing German Confederation.
Prussia and Austria signed the Peace (Treaty) of Prague, ending the Seven Weeks’ War. Austria accepted the dissolution of the German Confederation and was effectively excluded from future German political leadership, while Prussia was positioned to reorganize Germany under its influence. The treaty also addressed the Schleswig-Holstein settlement and linked Austria’s loss of Venetia to Italy through French mediation.
Austria and Italy signed the Treaty of Vienna, formally concluding the Third War of Italian Independence. The agreement confirmed the transfer of Venetia (via France and a plebiscite process described in many accounts) to Italy. Together with the Peace of Prague, this helped lock in the new balance of power: Austria pulled back from both Germany and much of northern Italy, while Prussia’s path toward German unification became clearer.
Austro-Prussian War (Seven Weeks' War) and the Treaty of Prague (1866)