Second Siege of Vienna

In 1683, an Ottoman army besieged the Habsburg capital of Vienna for two months before a relief force of Imperial, Polish-Lithuanian, and German troops broke the siege in a decisive battle on 12 September. The Ottoman defeat did not end the empire's power overnight, but it marked a turning point. Over the following sixteen years, the Habsburgs and their allies pushed the Ottomans out of most of Hungary, reversing a century and a half of Ottoman expansion in Central Europe.

The background lay in a long rivalry between the Ottoman Empire and the Habsburg monarchy. The Ottomans had taken most of Hungary after the Battle of Mohács in 1526 and had besieged Vienna once before, unsuccessfully, in 1529. A long truce held through the early 1680s, but tensions persisted, fueled by unrest among Hungarian nobles resisting Habsburg rule. The Ottoman grand vizier, Kara Mustafa Pasha, saw an opportunity. Backed by Sultan Mehmed IV, he assembled a very large army in 1683 and marched north. Estimates of its size vary widely, and historians generally treat the larger contemporary figures with caution.

Emperor Leopold I fled Vienna as the Ottoman forces approached, leaving the city's defense to a garrison under Count Ernst Rüdiger von Starhemberg. The siege began in July. Ottoman engineers dug trenches and mines under the fortifications, while disease and hunger weakened the defenders. Vienna was close to falling by early September. Kara Mustafa has often been criticized for choosing to wear the city down rather than storm it, perhaps hoping to preserve its wealth, though his exact reasoning is uncertain.

Meanwhile, Leopold had secured help from Pope Innocent XI and from King John III Sobieski of Poland-Lithuania. A combined army, with Sobieski in overall command, gathered on the heights of the Kahlenberg above the city. On 12 September they attacked, and a large cavalry charge, including the Polish heavy cavalry known as hussars, helped shatter the Ottoman lines. The besiegers fled, leaving behind much of their equipment. Kara Mustafa withdrew southeast and was executed on the sultan's orders in Belgrade later that year.

The victory encouraged the formation of the Holy League in 1684, uniting the Habsburgs, Poland-Lithuania, Venice, and later Russia against the Ottomans. Buda fell in 1686, and the Ottoman defeat at the Battle of Zenta in 1697 led to the Treaty of Karlowitz in 1699, in which the Ottomans ceded Hungary and Transylvania to the Habsburgs. The Ottoman Empire remained a major power for generations, but its position in Europe was now defensive, and the Habsburgs emerged as the leading force in southeastern Europe.