In the summer of 1683 the Ottoman army led by Grand Vizier Kara Mustapha laid siege to Vienna, the Emperor’s official residence and capital city. Up to 200,000 soldiers were encamped before the walls. Along with many of its inhabitants, Emperor Leopold I had already fled. Help came from an imperial army commanded by Duke Charles V of Lorraine, who joined up with units from other parts of the Holy Roman Empire and the troops of Jan III Sobieski, the King of Poland. Together they beat back the Ottoman army and lifted the siege.