In 1815 Prussia emerged from the Great Wars against France and Napoleon as one of the leading powers in Europe
At this time most of the other German territories were minor principalities and duchies that became known as the German Confederation.
Austria had a much greater influence over this assembly than did Prussia.
Otto von Bismarck was a successful Prussian statesman who orchestrated several wars in order to create firstly the North German Confederation under Prussian leadership, and then later a unified German Empire with the Prussian King Wilhelm I as it's emperor.
1866 Austro-Prussian War
1870 Franco-Prussian War
In 1863 Frederick VII of Denmark died and was succeeded by Christian IX who claimed the duchies of Schleswig and Holstein. They were also claimed by a German duke called Frederick von Augustenburg.
Southern Schleswig and Holstein were German speaking. Bismarck objected to Schleswig being annexed by Denmark and demanded that it be returned to its former status. When Denmark refused, Prussia and Austria decided to settle the issue by force of arms and made Denmark cede both territories.
It was planned that the Diet of the German Confederation would decide who would rule Schleswig-Holstein but Bismarck made a secret agreement with Austria known as the Gastein Convention whereby Austria received Holstein and Prussia received Schleswig.
Bismarck wanted to unify Germany. Austria was traditionally the leader of the Germanic peoples. Bismarck knew that Austria had to be excluded in order for Prussia to become the lead state in a unified Germany.
In 1866 Bismarck claimed that Austria had broken the Gastein Convention and deliberately provoked a war between Prussia and Austria using this as an excuse. Prussia demonstrated that it possessed a superior military organisation by overrunning Austria's German allies and defeating the Austrian army at Königgrätz (Sadowa).
At the Peace of Prague in 1866 the German Confederation was dissolved and Austria was made to cede territory to Prussia's ally Italy. Prussia annexed Frankfurt, Hanover, Nassau, Hesse-Cassel and Schleswig-Holstein. The other independent German states were forced into forming the North German Federation under Prussian control and Austria was formally excluded from playing any part in the future affairs of this new assembly.
The war lasted seven weeks and became known as the "Seven week war". It created a feeling in Prussia that the army was unbeatable.
Victory over Austria in 1866 increased tension between Prussia and France. Bismarck knew that the states of the North German Confederation would look to Prussia if they perceived France to be a threat. So Bismarck looked to use the tension in an effort to provoke France into initiating hostile action against Prussia.
In 1870 the German prince Leopold of Hohenzollern-Sigmaringen, a relative of Kaiser Wilhelm I, was offered the vacant throne of Spain. France blocked this appointment and Bismarck was quick to capitalise on it. He published the Ems Telegram, a carefully edited version of a conversation between the Prussian King and the French ambassador in Ems, in which the Prussian King, under threat of war, refused to guarantee that he would never approve the candidacy of a Hohenzollern to the Spanish throne.
French public opinion was enraged and France duly declared war on 19th July. France was seen as the aggressor and the German Confederation rallied to the Prussian cause. The war went very well for Prussia and, even whilst the war was still going on, Bismarck set about convincing the other German states that they should accept unification. On 18th January 1871 King Wilhelm I of Prussia was proclaimed as 'Emperor' of the new German Empire consisting of 25 states who retained some degree of self government.
Under the terms of the Treaty of Frankfurt signed on May 10, 1871, France was forced to give up the territory of Alsace and part of Lorraine and pay a huge sum of money in reparations.
The Hapsburg Empire (Austria) was weakened and in 1867, the year after the Austro-Prussian War, became the Austro-Hungarian dual monarchy.
It gave France a desire for vengeance and a reason to form an alliance with Russia.
Prussia became the head of a very powerful new state, Germany, and tended to dominate the fellow Germanic Austrians.