Ferdinand set out to enforce his claim on Hungary and captured Buda in 1527, only to relinquish his hold on it in 1529 when an Ottoman counter-attack stripped Ferdinand of all his territorial gains. įollowing the Diet of Pozsony (modern Bratislava) on 26 October, Ferdinand was declared king of Royal Hungary due to the agreement between his and Louis's families, cemented by Ferdinand's marriage to Louis's sister Anna and Louis's marriage to Ferdinand's sister Mary. Thus Hungary became divided into three zones: Royal Hungary, Ottoman Hungary and the Principality of Transylvania, an arrangement which persisted until 1700. Ferdinand won recognition only in western Hungary a noble called John Zápolya, from a power-base in Transylvania, challenged him for the crown and was recognised as king by Suleiman in return for accepting vassal status within the Ottoman Empire. His brother-in-law, Archduke Ferdinand I of Austria, brother of Holy Roman Emperor Charles V, claimed the vacant Hungarian throne. In August 1526, Sultan Suleiman I decisively defeated the forces of King Louis II of Hungary at the Battle of Mohács, paving the way for the Ottomans to gain control of south-eastern Hungary the childless King Louis died, possibly drowning when he attempted to escape the battlefield. Main articles: Battle of Mohács and Hungarian campaign of 1527–1528 The failure of the siege of Vienna marked the beginning of 150 years of bitter military tension between the Habsburgs and Ottomans, punctuated by reciprocal attacks, and culminating in a second siege of Vienna in 1683. Some scholars suggest Suleiman intended to use Hungary as a staging ground for further invasion of Europe. Some modern historians suggest that Suleiman's primary objective was to assert Ottoman control over all of Hungary, including the western part (known as Royal Hungary) that was then still under Habsburg control. Historians offer conflicting interpretations of the Ottoman's long-term goals, including the motivations behind the choice of Vienna as the campaign's immediate target. The Ottoman attack on Vienna was part of the empire's intervention into the Hungarian conflict, and in the short term sought to secure Zápolya's position. Zápolya would eventually seek aid from, and become a vassal of the Ottoman Empire, after Ferdinand began to take control of western Hungary, including the city of Buda. Following Louis' death, rival factions within Hungary selected two successors: Archduke Ferdinand I of Austria, supported by the House of Habsburg, and John Zápolya.

The siege came in the aftermath of the 1526 Battle of Mohács, which had resulted in the death of Louis II, King of Hungary, and the descent of the kingdom into civil war. Nevertheless, Vienna was able to survive the siege, which ultimately lasted just over two weeks, from 27 September to 15 October, 1529. Suleiman the Magnificent, sultan of the Ottomans, attacked the city with over 100,000 men, while the defenders, led by Niklas Graf Salm, numbered no more than 21,000. The siege of Vienna, in 1529, was the first attempt by the Ottoman Empire to capture the capital city of Vienna, Austria, Holy Roman Empire.

Siege of vienna opening bombardment