That man's son, the second holder of this name, was succeeded in death by the election of Henry of Valois and bore the nickname Augustus.  
The first of the kings of a certain nation to bear this name gained the throne a year after his predecessor's parliament-empowering decree of "Nihil Novi," and rewarded a loyalty oath from Albert of Brandenburg by making him the first Duke of Prussia.  That man's son, the second holder of this name, was succeeded in death by the election of Henry of Valois and bore the nickname Augustus.  That man's grandson, the third holder of the name, was defeated at Stangebro in 1598, costing him the Swedish throne.  This is also the name of a single Holy Roman Emperor, whose forces were routed at the Battle of Nicopolis during his tenure as the King of Hungary and who helped organize the Council of Constance.  FTP, give this name held by three Polish kings, the last of whom invaded Russia during the Time of Troubles.
The first of the kings of a certain nation to bear this name gained the throne a year after his predecessor's parliament-empowering decree of "Nihil Novi," and rewarded a loyalty oath from Albert of Brandenburg by making him the first Duke of Prussia.  
Sigismund or Zygmunt