Ferdinand I  Ferdinand I, 1503–64, Holy Roman emperor (1558–64),
king of Bohemia (1526–64) and of Hungary (1526–64), younger
brother of Holy Roman Emperor Charles V. Brought up in Spain, he
was expected to succeed his grandfather, Ferdinand II of Aragón,
who, instead, made Charles his heir. In 1521, Charles gave him
the Austrian duchies of the Hapsburgs. In the same year
Ferdinand married Anna, daughter of Uladislaus II, king of
Hungary and Bohemia, in fulfillment of a treaty (1515) between
his grandfather, Holy Roman Emperor Maximilian I, and Uladislaus
II. When Anna's brother Louis II, who succeeded to the thrones
of Bohemia and Hungary on his father's death (1516), was killed
at the battle of Mohacs (1526), Ferdinand claimed the
succession. He was elected king of Bohemia, but in Hungary he
met the rival claim of John I (John Zapolya), supported by
Sultan Sulayman I. John's claims were inherited by his son John
Sigismund (king as John II). The sporadic warfare in Hungary was
indecisive, except that Ferdinan