Two monarchies who ruled the Austro-Hungarian empire for half a century contolled one of Europe’s largest power back in the 19th century. The empire was founded in 1867 after Austria was beaten by Prussia in the “Seven Weeks War” which taken place a year earlier (1866).
Looking for Austrian political position support which was weak after the war, Franz Joseph I, Austrian caesar and Hungarian king, compromised with the Magyar aristocrate of Hungary.
The compromise resulted in the formation of Austro-Hungary empire that united 50 million people under Franz Joseph, also united the military power, international policy and financial system. Austria and Hungary however have a separate parliaments which controlled other ethnics and races in the empire.
Covering an area of 241,491 square miles (675,000 square km), the empire consisted of current independence states of: Austria; Czech, Republic; Hungary and Slovakia as well as some parts of Bosnia and Herzegovina, Croatia, Italy, Montenegro, Poland, Romania, Serbia and Slovenia.
Austro-Hungary had a quarrel with Russia and Sebia when the Ottoman empire (now Turkey) fell in the early 1900s. On 28 June 1914, Archduke Francis Ferdinand, the heir of the Austro-Hungary empire, was killed by a Serbian in Sarajevo, Bosnia.
A year after that, supported by Germany, Austro-Hungary declared a war with Serbia. The conflict spread that it became the first World War (WWI). It triggered alliance and and overlapping agreements between the European powers. At the end of the war, most of the Austro-Hungary members declared independence and eventually ended the empire.