information:classification
1526–1566: Conquest of the Kingdom of Hungary

Since 1360s Hungary confronted with the Ottoman Empire. The Kingdom of Hungary led several crusades, campaigns and carried out several defence battles and sieges against the Ottomans. Hungary bore the brunt of the Ottoman wars in Europe during the 15th century and successfully halted the Ottoman advance. From 1490, after the death of King Matthias of Hungary, the royal power declined. In 1521, Hungary was invaded by Sultan Suleiman the Magnificent, the border fortress Belgrade considered as the key and southern gate of the Kingdom of Hungary, after two previous sieges, the Ottomans captured this stronghold by the Third Siege of Belgrade. The Sultan launched an attack against the weakened kingdom, whose smaller army was defeated in 1526 at the Battle of Mohács and King Louis II of Hungary died.

After the Ottoman victory in the Battle of Mohács in 1526, only the southwestern part of the Kingdom of Hungary was actually conquered. The Ottoman campaign continued between 1526 and 1556 with small campaigns and major summer invasions – troops would return south of the Balkan Mountains before winter. In 1529, they mounted their first major attack on the Austrian Habsburg monarchy, attempting to conquer the city of Vienna (siege of Vienna). In 1532, another attack on Vienna with 60,000 troops in the main army was held up by the small fort (800 defenders) of Kőszeg in western Hungary, fighting a suicidal battle. The invading troops were held up until winter was close and the Habsburg Empire had assembled a force of 80,000 at Vienna. The Ottoman troops returned home through Styria, laying waste to the country.

In the meantime, in 1538, the Ottoman Empire invaded Moldavia. In 1541, another campaign in Hungary took Buda and Pest (which today together form the Hungarian capital Budapest) with a largely bloodless trick: after concluding peace talks with an agreement, troops stormed the open gates of Buda in the night. In retaliation for a failed Austrian counter-attack in 1542, the conquest of the western half of central Hungary was finished in the 1543 campaign that took both the most important royal ex-capital, Székesfehérvár, and the ex-seat of the cardinal, Esztergom. However, the army of 35–40,000 men was not enough for Suleiman to mount another attack on Vienna. A temporary truce was signed between the Habsburg and Ottoman Empires in 1547, which was soon disregarded by the Habsburgs.

In the major but moderately successful Ottoman campaign of 1552, two armies took the eastern part of central Hungary, pushing the borders of the Ottoman Empire to the second (inner) line of northern végvár s (border castles), which Hungary originally built as defence against an expected second Mongol invasion —hence, afterwards, borders on this front changed little. For Hungarians, the 1552 campaign was a series of tragic losses and some heroic (but pyrrhic) victories, which entered folklore—most notably the fall of Drégely (a small fort defended to the last man by just 146 men, and the siege of Eger. The latter was a major végvár with more than 2,000 men, without outside help. They faced two Ottoman armies, which were surprisingly unable to take the castle within five weeks. (The fort was later taken in 1596.) Finally, the 1556 campaign secured Ottoman influence over Transylvania (which had fallen under Habsburg control for a time), while failing to gain any ground on the western front, being tied down in the second (after 1555) unsuccessful siege of the southwestern Hungarian border castle of Szigetvár.

The Ottoman Empire conducted another major war against the Habsburgs and their Hungarian territories between 1566 and 1568. The 1566 siege of Szigetvár, the third siege in which the fort was finally taken, but the aged Sultan died, deterring that year's push for Vienna.