The Battle of Vienna took place at Kahlenberg Mountain near Vienna on 12 September 1683 after the imperial city had been besieged by the Ottoman Empire for two months.
The battle was fought by the Habsburg Monarchy, the Polish-Lithuanian Commonwealth and the Holy Roman Empire, under the command of King John III Sobieski against the invading Muslim Ottoman Empire and its vassal and tributary states.
The battle marked the first time Poland and the Holy Roman Empire had cooperated militarily against the Turks, and it is often seen as a turning point in history, after which “the Ottoman Turks ceased to be a menace to the Christian world”.
In the ensuing war that lasted until 1698, the Turks lost almost all of Hungary to the Holy Roman Emperor Leopold I. The battle was won by the combined forces of the Holy Roman Empire of the German Nations and the Polish–Lithuanian Commonwealth, the latter represented only by the forces of the Crown of the Kingdom of Poland (the march of the Lithuanian army was delayed, and they reached Vienna after it had been relieved).
The Viennese garrison was led by Ernst Rüdiger Graf von Starhemberg, an Austrian subject of Holy Roman Emperor Leopold I. The overall command was held by the senior leader, the King of Poland, John III Sobieski, who led the relief forces. The opposing military forces were those of the Ottoman Empire and Ottoman fiefdoms commanded by Grand Vizier Merzifonlu Kara Mustafa Pasha.
The Ottoman army numbered approximately 90,000 –300,000 men (according to documents on the order of battle found in Kara Mustafa’s tent, initial strength at the start of the campaign was 170,000 men).
They began the siege on 14 July 1683. The Turkish forces consisted, among other units, of 60 ortas of Janissaries (12,000 men paper-strength) with an observation army of c. 70,000 men watching the countryside.
The decisive battle took place on 12 September, after the united relief army had arrived. Historians suggest the battle marked the turning point in the Ottoman–Habsburg wars, a 300-year struggle between the Holy Roman and Ottoman Empires.
In fact, during the 16 years following the battle, the Austrian Habsburgs gradually recovered and dominated southern Hungary and Transylvania, which had been largely cleared of Turkish forces. The battle is also noted for including the largest known cavalry charge in history.