The success of the family arose from the steady accumulation of land, and loyalty both to the Roman Catholic Church and to the Habsburg Emperor, the latter factor being the most important. A consistent theme of Hungarian history was an ardent and sometimes violent wish to become free of Austrian rule, a wish that was finally fulfilled at the end of the First World War. The Esterházy princes were consistently loyal to the Habsburg monarchy, and on several occasions rendered vital services to it in times of crisis. These included the Turkish siege of Vienna in 1683, and the outright occupation of Vienna by Napoleon in 1809.