History of Austria
Austria was dominated by the House of Habsburg and House of Habsburg-Lorraine ("Haus Österreich") from 1273 to 1918. In 1808, when Emperor Francis II of Austria dissolved the Holy Roman Empire, Austria became the Austrian Empire, and was also part of the German Confederation until the Austro-Prussian War of 1866. In 1867, Austria formed a dual monarchy with Hungary: the Austro-Hungarian Empire (1867–1918). When this empire collapsed after the end of World War I in 1918, Austria was reduced to the main, mostly German-speaking areas of the empire (its current frontiers), and adopted the name The Republic of German-Austria. However the union and name were forbidden by the Allies at the Treaty of Versailles. This led to the creation of the First Austrian Republic (1918-1933).
Austria–Germany relations
Modern-day Austria and Germany were united until 1866: their predecessors were part of the Holy Roman Empire and the German Confederation until the unification of German states under Prussia in 1871, which excluded Austria. In 1918 after the end of World War I, Austria renamed itself the Republic of German-Austria in an attempt for union with Germany but this was forbidden by the Treaty of Saint-Germain-en-Laye (1919). In 1938, the Third Reich, led by Austrian-born Adolf Hitler, annexed Austria in the "Anschluss".