<P> Frederick I, also called Frederick Barbarossa, was crowned Emperor in 1155 . He emphasized the "Romanness" of the empire, partly in an attempt to justify the power of the Emperor independent of the (now strengthened) Pope . An imperial assembly at the fields of Roncaglia in 1158 reclaimed imperial rights in reference to Justinian's Corpus Juris Civilis . Imperial rights had been referred to as regalia since the Investiture Controversy but were enumerated for the first time at Roncaglia . This comprehensive list included public roads, tariffs, coining, collecting punitive fees, and the investiture or seating and unseating of office holders . These rights were now explicitly rooted in Roman Law, a far - reaching constitutional act . </P> <P> Frederick's policies were primarily directed at Italy, where he clashed with the increasingly wealthy and free - minded cities of the north, especially Milan . He also embroiled himself in another conflict with the Papacy by supporting a candidate elected by a minority against Pope Alexander III (1159--81). Frederick supported a succession of antipopes before finally making peace with Alexander in 1177 . In Germany, the Emperor had repeatedly protected Henry the Lion against complaints by rival princes or cities (especially in the cases of Munich and Lübeck). Henry gave only lackluster support to Frederick's policies, and in a critical situation during the Italian wars, Henry refused the Emperor's plea for military support . After returning to Germany, an embittered Frederick opened proceedings against the Duke, resulting in a public ban and the confiscation of all his territories . In 1190, Frederick participated in the Third Crusade and died in the Armenian Kingdom of Cilicia . </P> <P> During the Hohenstaufen period, German princes facilitated a successful, peaceful eastward settlement of lands that were uninhabited or inhabited sparsely by West Slavs . German speaking farmers, traders, and craftsmen from the western part of the Empire, both Christians and Jews, moved into these areas . The gradual Germanization of these lands was a complex phenomenon that should not be interpreted in the biased terms of 19th - century nationalism . The eastward settlement expanded the influence of the empire to include Pomerania and Silesia, as did the intermarriage of the local, still mostly Slavic, rulers with German spouses . The Teutonic Knights were invited to Prussia by Duke Konrad of Masovia to Christianize the Prussians in 1226 . The monastic state of the Teutonic Order (German: Deutschordensstaat) and its later German successor state of Prussia were, however, never part of the Holy Roman Empire . </P> <P> Under the son and successor of Frederick Barbarossa, Henry VI, the Hohenstaufen dynasty reached its apex . Henry added the Norman kingdom of Sicily to his domains, held English king Richard the Lionheart captive, and aimed to establish a hereditary monarchy when he died in 1197 . As his son, Frederick II, though already elected king, was still a small child and living in Sicily, German princes chose to elect an adult king, resulting in the dual election of Frederick Barbarossa's youngest son Philip of Swabia and Henry the Lion's son Otto of Brunswick, who competed for the crown . Otto prevailed for a while after Philip was murdered in a private squabble in 1208 until he began to also claim Sicily . </P>

When did prussia leave the holy roman empire
find me the text answering this question