Territorial evolution of the Ottoman Empire
Suleiman I ( "Süleymān", ; almost always "Kanuni Sultan Süleyman") (6 November 1494  – 5/6/7 September 1566), was the tenth and longest-reigning Sultan of the Ottoman Empire, from 1520 to his death in 1566. Suleiman became a prominent monarch of 16th century Europe. Suleiman personally led Ottoman armies to conquer the Christian strongholds of Belgrade, Rhodes, and most of Hungary. In 1541 he annexed central Hungary while Transylvania became an Ottoman vassal. However rest of the Kingdom of Hungary including western and northern (Upper) Hungary and Croatia still were Habsburgs possessions. Suleiman also conquered Iraq in his conflict with the Safavid dynasty. Under his rule, the Ottoman fleet dominated the seas from the Mediterranean to the Red Sea and the Persian Gulf.
Ottoman Hungary
Instigating war by feigned diplomatic insult, Suleiman the Magnificent (1520–1566) attacked the Kingdom of Hungary and captured Belgrade in 1521. He did not hesitate to launch an attack against the weakened kingdom, whose smaller, badly led army (approximately 26,000 Hungarian soldiers compared to 45,000 Ottoman soldiers) was defeated on 29 August 1526 at the Battle of Mohács. Thus he became influential in the Kingdom of Hungary, while his semi-vassal, named John Zápolya and his enemy Ferdinand I both claimed the throne of the Kingdom. Suleiman went further and tried to crush Austrian forces, but his Siege of Vienna in 1529 failed after the onset of winter forced his retreat. The title of king of Hungary was disputed between Zápolya and Ferdinand until 1540. After the seizure of Buda by the Ottomans in 1541, the West and North recognized a Habsburg as king ("Royal Hungary"), while the central and southern counties were annexed by the Ottoman Sultan and the east was ruled by the son of Zápolya under the name Eastern Hungarian Kingdom which after 1570 became the Principality of Transylvania. Whereas a great many of the 17,000 and 19,000 Ottoman soldiers in service in the Ottoman fortresses in the territory of present-day Hungary were Orthodox and Muslim Balkan Slavs, Southern Slavs were also acting as akıncıs and other light troops intended for pillaging in the territory of present-day Hungary.
In these times, territory of present-day Hungary began to undergo changes due to the Ottoman occupation. Vast lands remained unpopulated and covered with woods. Flood plains became marshes. The life of the inhabitants on the Ottoman side was unsafe. Peasants fled to the woods and marshes, forming guerrilla bands, known as the Hajdú troops. Eventually, the territory of present-day Hungary became a drain on the Ottoman Empire, swallowing much of its revenue into the maintenance of a long chain of border forts. However, some parts of the economy flourished. In the huge unpopulated areas, townships bred cattle that were herded to south Germany and northern Italy - in some years they exported 500,000 head of cattle. Wine was traded to the Czech lands, Austria and Poland.