Austrians
Historically, Austrians were regarded as ethnic Germans and viewed themselves as such. Austria was part of the Holy Roman Empire and the German Confederation until the Austro-Prussian war in 1866 which resulted in Prussia expelling Austria from the Confederation. Thus, when Germany was founded as a nation-state in 1871, Austria was not a part of it. In 1867, Austria was reformed into the Austro-Hungarian Empire. After the collapse of the Austro-Hungarian Empire in 1918 at the end of World War I, Austria was reduced to a rump state and adopted and briefly used the name the Republic of German-Austria ("Republik Deutschösterreich") in an attempt for union with the Republic of Germany, but was forbidden due to the Treaty of Saint-Germain-en-Laye (1919). The First Austrian Republic was founded in 1919. The Third Reich annexed Austria with the "Anschluss" in 1938.
Karl Seitz
Seitz entered history in 1918, when Austria-Hungary was breaking down, and its disintegration into smaller independent nation states was becoming manifest. On October 21, the Imperial Council members representing the empire's ethnically-German provinces moved to form a Provisional National Assembly for their paralyzed rump state. In its constituent session, the Provisional National Assembly appointed Seitz as one of its three chairmen. Barely more than a week later, by October 30, Seitz had informally emerged as an acting head of state. By November 12, Emperor Karl had abdicated, and the Republic of German Austria had been proclaimed. Seitz had thus turned from acting head of state to provisional president.