In a historical context, Czech texts use the term to refer to any territory ruled by the Kings of Bohemia, i.e., the lands of the Bohemian Crown (země Koruny české) as established by Emperor Charles IV in the 14th century. This would include territories like the Lusatias (which in 1635 fell to Saxony) and the whole of Silesia, all ruled from Prague Castle at that time. After the conquest of Silesia by the Prussian king Frederick the Great in 1742, the remaining lands of the Bohemian Crown—Bohemia, Moravia and Austrian Silesia—have been more or less co-extensive with the territory of the modern-day Czech Republic.[citation needed]