John III Sobieski’s greatest and most famous achievement came in 1683 during the Battle of Vienna. At this time, the Ottoman Empire, under Sultan Mehmed IV, had launched a massive invasion of Central Europe, with its army laying siege to Vienna, the capital of the Habsburg Monarchy. The fall of Vienna would have opened the gates for the Ottomans to further penetrate Europe, posing an existential threat to the Christian states of the continent.
In response to this crisis, Leopold I, the Holy Roman Emperor, called on European leaders for help. John III Sobieski, as the king of Poland, answered this call. Leading a coalition of European forces, Sobieski marched his army—famously including the Winged Hussars, Poland’s elite cavalry unit—across the Carpathian Mountains to relieve the besieged city.
On September 12, 1683, Sobieski and his allies launched a surprise attack on the Ottoman forces. The charge of the Winged Hussars, led by Sobieski himself, broke the Ottoman lines and led to a decisive victory for the European coalition. The Ottomans retreated in disarray, and Vienna was saved.
For his leadership and bravery, Sobieski earned the nickname “The Lion of Lechistan” from the Ottomans and was hailed as the savior of Christian Europe. Pope Innocent XI even referred to him as the “Defender of the Faith.” The victory at Vienna not only secured Europe from Ottoman conquest but also marked the beginning of the empire's long decline.