The Battle of Vienna, also known as the Siege of Vienna, was the first major battle of the Great Turkish War between the Muslim Turkish Ottoman Empire and the Roman Catholic "Holy League", fought near the Austrian capital of Vienna in 1683. The miraculous Christian victory over the Turks at Vienna ended the Ottoman Empire's threat to the Christian world, and the ensuing war, which ended in 1699, would see the Ottoman Empire lose Hungary to the Holy Roman Empire.
In 1681, Holy Roman Emperor Leopold I's pursuit of Counter-Reformation principles resulted in the outbreak of a Protestant Hungarian rebellion led by Imre Thokoly. The Ottoman Empire, which had unsuccessfully attempted to capture Vienna in 1529, capitalized on this internal unrest within the Holy Roman Empire to send forces to aid the Hungarian rebels; the Ottomans also recognized Imre as King of "Upper Hungary", a principality which included eastern Slovakia and northwestern Hungary. After Habsburg forces trespassed on Hungarian soil to battle the Hungarian rebels, the Ottoman Empire mobilized its army on 21 January 1682 and declared war on the Habsburgs on 6 August 1682. However, the Ottomans waited 15 months for their great invasion, enabling Emperor Leopold to prepare Vienna's defenses. In 1683, the Holy Roman Empire concluded a defensive alliance with Poland-Lithuania, guaranteeing the dispatch of a Polish relief army if Vienna was ever attacked. On 31 March 1683, the Ottoman army's advance guard left Rumelia, and the Ottoman army reached Belgrade in May 1683; they were joined by 40,000 Crimean Tatar soldiers, Hungarian rebels, and Romanian allies. On 14 July 1683, the main Ottoman army arrived at Vienna, which was held by Count Ernst Rudiger von Starhemberg's 15,000 Habsburg troops; Emperor Leopold and 60,000 Viennese civilians relocated to Passau, while Duke Charles V of Lorraine withdrew to Linz with 20,000 troops. On 15 August 1683, King Jan Sobieski of Poland-Lithuania left Krakow to come to Austria's aid, leaving his nation virtually defenseless in the process. On 6 September, the Poles crossed the Danube 19 miles northwest of Vienna, uniting with Imperial forces and reinforcements from Saxony, Bavaria, Baden, Franconia, and Swabia, as well as by Cossack mercenaries. King Jan Sobieski was appointed to command the allied army of 80,000 troops against the 150,000 Ottomans.
In early September, the Ottomans nearly breached Vienna's walls through tunneling, in spite of the Viennese populations' efforts to counter-tunnel. On 12 September 1683, the Ottomans launched their assault on Vienna, but Charles of Lorraine ordered a counterattack which nearly broke through the Ottoman lines. The Ottomans failed to take Vienna before Sobieski arrived with the relief army, and the Ottomans focused on capturing the city rather than holding off the Polish reinforcements. At 4:00 PM, the Polish cavalry charged the Ottomans' central position, obliterating their lines and forcing the Ottoman Vizier Kara Mustafa Pasha to flee. At 6:00 PM, three Polish cavalry groups and one German group, totalling some 18,000 horsemen, engaged in the largest cavalry charge in history, with Sobieski personally leading the famous charge of 3,000 Polish "Winged Hussars". The Poles easily broke through the Ottoman lines, and the exhausted and demoralized Ottomans soon began to flee from the battlefield. The Ottomans suffered their worst defeat since the rise of their empire in 1299, and the Christian armies seized large quantities of booty, including tents, sheep, cattle, and camels. On 25 December, Kara Mustafa was executed by his Janissaries in Belgrade by strangulation with a silk rope.
The Christian victory at Vienna would enable Sobieski to liberate northwestern Hungary after the Battle of Parkany, while Charles of Lorraine took Belgrade and most of Serbia in 1686, and southern Hungary and Transylvania were conquered in 1687. Ottoman imperial expansion into Europe was ended by the disastrous defeat at Vienna. In addition, the croissant was invented in Vienna to commemorate the defeat of the Ottomans, whose flag bore a prominent crescent; many bags of coffee were captured from the abandoned Ottoman encampment, and they were used by Franciszek Jerzy Kulczycki to establish the first coffeehouse in Vienna, which combined sugar and milk with coffee and called it a cappuccino in honor of the Capuchin monk Marco d'Aviano, who had inspired the defenders during the siege.