Habsburg was a family of dukes, kings, and monarchs. They were very important in European history. They ruled Austria, later Austria-Hungary for more than 600 years. They also sometimes owned Spain, the Netherlands, and the Holy Roman Empire from about 1280 to 1918.
A Treaty was made in Vienna in 1515 between the king of Poland and duke of Lithuania from the Jagiellon dynasty and the duke of Austria from the Habsburg family. It said that if the kings of Bohemia and Hungary, (Jagiellons), were to die without male heirs the Duke of Austria would take over their territory.