The key events during his reign were the conflict with the Ottoman Empire, which in the 1520s began a great advance into Central Europe, and the Protestant Reformation, which resulted in several wars of religion.

Although not a military leader, Ferdinand was a capable organizer with institutional imagination who focused on building a centralized government for Austria, Hungary, and Bohemia instead of striving for universal monarchy.

[3][4] He reintroduced major innovations of his grandfather Maximilian I such as the Hofrat (court council) with a chancellery and a treasury attached to it (this time, the structure would last until the reform of Maria Theresa) and added innovations of his own such as the Raitkammer (collections office) and the Hofkriegsrat, conceived to counter the threat from the Ottoman Empire, while also successfully subduing the most radical of his rebellious Austrian subjects and turning the political class in Bohemia and Hungary into Habsburg partners.

He shared the same name, birthday (March 10th), culture and customs with his maternal grandfather, Ferdinand II of Aragon and became the latter’s favorite grandchild, their own mothers also had the same name, Juana Enriquez and Joanna of Castile.

Ferdinand returned in command of his brother's fleet but en route was blown off-course and spent four days in Kinsale in Ireland before reaching his destination.

With the death of his grandfather Maximilian I and the accession of his now 19-year-old brother, Charles V, to the title of the Holy Roman Emperor in 1519, Ferdinand was entrusted with the government of the Austrian hereditary lands, roughly modern-day Austria and Slovenia.

According to the terms set at the First Congress of Vienna in 1515, Ferdinand married Anne Jagiellonica, daughter of King Vladislaus II of Hungary and Bohemia on 22 July 1515.

On 24 October 1526 the Bohemian Diet, acting under the influence of chancellor Adam of Hradce, elected Ferdinand king of Bohemia under conditions of confirming traditional privileges of the estates and also moving the Habsburg court to Prague.

Ferdinand also had the support of his brother, the Emperor Charles V. On 10 November 1526, John Zápolya was proclaimed king by a Diet at Székesfehérvár, elected in the parliament by the untitled lesser nobility (gentry).

[20] In return for the throne, King Ferdinand promised to respect the historic rights, freedoms, laws and customs of the Croats when they united with the Hungarian kingdom and to defend Croatia from Ottoman invasion.

He told the Austrian Landtag, the assembled representatives of the nobility, at Linz in 1530 that 'the Turks cannot be resisted unless the Kingdom of Hungary was in the hands of an Archduke of Austria or another German prince'.

"[21] The Austrian lands were in miserable economic and financial conditions, but Ferdinand was forced to introduce the so-called Turk Tax (Türkensteuer) to finance his campaign against the Ottoman threat.

His annual revenues only allowed him to hire 5,000 mercenaries for two months; thus Ferdinand asked for help from his brother, Emperor Charles V, and started to borrow money from rich bankers like the Fugger family.

As long as he hoped for a favorable response from his humiliating overtures to Suleiman, Ferdinand was not inclined to grant the peace which the Protestants demanded at the Diet of Regensburg which met in April 1532.

Those who had up to this time joined the Reformation obtained religious liberty until the meeting of a council and in a separate compact all proceedings in matters of religion pending before the imperial chamber court were temporarily paused.

Despite these enormous territorial and demographic losses, the smaller, heavily war-torn Royal Hungary had remained economically more important to the Habsburg rulers than Austria or Kingdom of Bohemia even at the end of the 16th century.

[30] At the conference, which opened on 5 February, Ferdinand cajoled, persuaded and threatened the various representatives into agreement on three important principles promulgated on 25 September: After 1555, the Peace of Augsburg became the legitimating legal document governing the co-existence of the Lutheran and Catholic faiths in the German lands of the Holy Roman Empire, and it served to ameliorate many of the tensions between followers of the "Old Faith" (Catholicism) and the followers of Luther, but it had two fundamental flaws.

First, Ferdinand had rushed the article on reservatum ecclesiasticum through the debate; it had not undergone the scrutiny and discussion that attended the widespread acceptance and support of cuius regio, eius religio.

The Declaratio Ferdinandei was not debated in plenary session at all; using his authority to "act and settle,"[30] Ferdinand had added it at the last minute, responding to lobbying by princely families and knights.

[32] While these specific failings came back to haunt the empire in subsequent decades, perhaps the greatest weakness of the Peace of Augsburg was its failure to take into account the growing diversity of religious expression emerging in the so-called evangelical and reformed traditions.

[33] Some historians maintain Ferdinand had also been touched by the reformed philosophies, and was probably the closest the Holy Roman Empire ever came to a Protestant emperor; he remained nominally a Catholic throughout his life, although reportedly he refused last rites on his deathbed.

In the Netherlands, Philip's ascension in Spain raised particular problems; for the sake of harmony, order, and prosperity Charles had not blocked the Reformation, and had tolerated a high level of local autonomy.

An important invention of Ferdinand was the Hofkriegsrat (Aulic War Council), officially established in 1556 to coordinate military affairs in all Habsburg lands (inside and outside the Holy Roman Empire).

As the ruler of Austria, Bohemia and Royal Hungary, Ferdinand adopted a policy of centralisation and, in common with other monarchs of the time, the construction of an absolute monarchy.

In 1527, soon after ascending the throne, he published a constitution for his hereditary domains (Hofstaatsordnung) and established Austrian-style institutions in Pressburg for Hungary, in Prague for Bohemia, and in Breslau for Silesia.

Though lacking resources, he managed to defend his land against the Ottomans with limited support from his brother, and even secured a part of Hungary that would later provide the basis for the conquest of the whole kingdom by the Habsburgs.

[55] His handling of the Protestant Reformation proved more flexible and more effective than that of his brother and he played a key part in the settlement of 1555, which started an era of peace in Germany.

Fichtner remarks that Ferdinand was a mediocre military commander (thus the many difficulties in dealing with the Ottomans in Hungary) but an energetic and very imaginative administrator, who produced a framework for his empire that endured into the eighteenth century.

He also called Jesuits to the capital city, attracted architects and scholars from Italy and the Low Countries to create an intellectual milieu surrounding the court.

[17] They had fifteen children, all but two of whom reached adulthood: In 1556 Ferdinand inherited the thrones of the Holy Roman Empire and the vast realms of Central and Eastern Europe from his brother Charles V went as following: "His Imperial and Royal Majesty, Ferdinand I, by the Grace of God elected Holy Roman Emperor, forever Augustus, King of Germany, King of Hungary, of Bohemia, of Dalmatia, of Croatia, of Slavonia, of Galicia, of Lodomeria, of Italy, of Cumania, of Bulgaria, of Serbia, of Rama, of Romania, etc.