By 1525 France had turned its attention to the conquering of the rich Italian Duchy of Milan, opposed or assisted at varying times by Italian states, with both sides calling upon the support of Swiss, German and Italian mercenaries. In these campaigns France's toughest adversary was the Spanish army, and when the thrones of Spain and Austria were combined in 1519, it altered the whole nature of the Italian Wars. In the titanic clash at Pavia the French were smashed by the Imperial army, King Francis I captured and the cream of his nobility slaughtered.