Ferdinand, in addition to the lands he receives from his brother, also increases his territorial reach by marrying into the Jagiellon family, the royal family of Hungary and Bohemia.

When his brother-in-law, King Louis, dies fighting the Turks at the Battle of Mohacs in 1526, Ferdinand claims the right of succession.

Although the diets representing the nobility of Bohemia (and its dependencies of Moravia and Silesia) do not acknowledge Ferdinand's hereditary rights, they formally elect him king of Bohemia.

As king of Bohemia, he also becomes an elector-prince of the Holy Roman Empire.

In Hungary and in the subordinate Kingdom of Croatia-Slavonia-Dalmatia, however, Ferdinand faces the rival claim of a Hungarian nobleman and the reality of the Turkish conquest of the country.

He is able to assert authority only over the northern and western edges of the country, which becomes known as Royal Hungary.

His Hungarian rival becomes a vassal of the Turks, ruling over Transylvania in eastern Hungary.

The rest of Hungary will become part of the Ottoman Empire in 1603.

Although Ferdinand undertakes various administrative reforms in order to centralize authority and increase his power, no meaningful integration of the Hereditary Lands and the two newly acquired kingdoms occurs.

In contrast to the authority of kings of Western Europe, where feudal structures are already in decline, Ferdinand's authority continues to rest on the consent of the nobles as expressed in the local diets, which successfully resist administrative centralization.