Austria-Hungary, or the Austro-Hungarian Empire, known also as the 'dual monarchy', was the final form adopted by the Hapsburg or Austrian Empire in central Europe. The empire was in 1867 reorganised to incorporate two monarchic entities, the Austrian empire (incorporating modern Austria, Bohemia, Moravia, the South Tyrol, Slovenia, Dalmatia and the Lemberg (Lviv) region of western Ukraine) and the Kingdom of Hungary (Hungary, Slovakia, Transylvania, and Croatia. The two monarchies were united under single monarch, and although Austria and Hungary had separate governments for domestic purposes, they were a single nation on the international stage. The reorganisation had taken place in an attempt to ease the strains within the monolithic Austrian Empire between the various national groups (indeed, the 'dual monatrchy' Austro-Hungarian model was for a time advocated by early Sinn Fein as a way of solving the disputes between Ireland and Great Britain). However, it failed to satisfy the aspirations of the smaller national groupings in the em,pire, and indeed the Hungarian government, once freed of control from Vienna, itself attempted to 'Hungarianise' the Romanian, Slovak, Serb and Croat minorities within its borders.
Under such strains, he dual monarchy system could not survive the shock of defeat in the First World War. The empire broke up into a number of separate sovereign states and areas annexed to neighbouring states; this was formalised by treaties made in 1919-20.
The following states emerged from the Austro-Hungarian Empire in the 1918-20 period: Austria, Hungary, Czechoslovakia. Land formerly part of the empire was also annexed by Italy, Yugoslavia, Romania and Poland.