After the Ottoman victory in the Battle of Mohács in 1526, only the southwestern part of the Kingdom of Hungary was actually conquered. The Ottoman campaign continued between 1526 and 1556 with small campaigns and major summer invasions – troops would return south of the Balkan Mountains before winter. In 1529, they mounted their first major attack on the Austrian Habsburg Monarchy, attempting to conquer the city of Vienna (siege of Vienna). In 1532, another attack on Vienna with 60,000 troops in the main army was held up by the small fort (800 defenders) of "Kőszeg" in western Hungary, fighting a suicidal battle. The invading troops were held up until winter was close and the Habsburg Empire had assembled a force of 80,000 at Vienna. The Ottoman troops returned home through Styria, laying waste to the country.