The division of the Habsburg territories between the elder Albertinian and the younger Leopoldian line occurred after the early death of Duke Rudolf IV in 1365, when his surviving brothers Albert III and Leopold III, after several years of joint rule, divided the dynasty's dominions. The Leopoldian line received the Duchy of Styria, ruled by Austria according to the 1186 Georgenberg Pact, as well as the duchies of Carinthia and Duchy of Carniola, the County of Tyrol, and the original Habsburg estates in the former Duchy of Swabia.
Duke Leopold had four sons; upon his death in 1386 he was initially succeeded by the eldest, William the Courteous, who ten years later had to cede Tyrol and the Swabian estates to the second-born son Leopold IV. Upon William's death in 1406, the remaining territories of Styria, Carinthia and Carniola were inherited by the third-born Ernest the Iron and became known as Inner Austria. Tyrol fell to the youngest brother, Frederick IV, called 'of the Empty Pockets'.
Only the two youngest sons of Leopold III, Ernest the Iron and Frederick IV, had issue. The children of Ernest and his wife, the Piast princess Cymburgis of Masovia, started the most famous line of the Habsburg dynasty to which most subsequent Holy Roman Emperors belonged, including their son Frederick III (V), who officially acknowledged the Austrian archducal title and by 1490 had re-unified all the dynasty's dominions. His descendants, among them Maximilian I and Charles V, ruled the Holy Roman Empire and the Austrian Habsburg Monarchy in an unbroken succession until the male line became extinct with the death of Emperor Charles VI in 1740. The line of succession was continued by the last "genuine" Habsburg ruler, Maria Theresa, who became ancestress of the Imperial House of Lorraine.