Frederick II , Holy Roman Emperor Frederick II ( 26 December 1194 – 13 December 1250 ) , was one of the most powerful Holy Roman Emperors of the Middle Ages and head of the House of Hohenstaufen . His political and cultural ambitions , based in Sicily and stretching through Italy to Germany , and even to Jerusalem , were enormous ; however , his enemies , especially the popes , prevailed , and his dynasty collapsed soon after his death . Historians have searched for superlatives to describe him , as in the case of Professor Donald Detwiler , who wrote : Viewing himself as a direct successor to the Roman Emperors of Antiquity , he was Emperor of the Romans from his papal coronation in 1220 until his death ; he was also a claimant to the title of King of the Romans from 1212 and unopposed holder of that monarchy from 1215 . As such , he was King of Germany , of Italy , and of Burgundy . At the age of three , he was crowned King of Sicily as a co - ruler with his mother , Constance of Hauteville , the daughter of Roger II of Sicily . His other royal title was King of Jerusalem by virtue of marriage and his connection with the Sixth Crusade . He was frequently at war with the Papacy , hemmed in between Frederick ' s lands in northern Italy and his Kingdom of Sicily ( the " Regno " ) to the south , and thus he was excommunicated four times and often vilified in pro - papal chronicles of the time and since . Pope Gregory IX went so far as to call him the Antichrist . Speaking six languages ( Latin , Sicilian , German , French , Greek and Arabic ) , Frederick was an avid patron of science and the arts . He played a major role in promoting literature through the Sicilian School of poetry . His Sicilian royal court in Palermo , from around 1220 to his death , saw the first use of a literary form of an Italo - Romance language , Sicilian . The poetry that emanated from the school had a significant influence on literature and on what was to become the modern Italian language . The school and its poetry were saluted by Dante and his peers and predate by at least a century the use of the Tuscan idiom as the elite literary language of Italy . After his death , his line quickly died out and the House of Hohenstaufen came to an end . King of Italy . Early years . Born in Iesi , near Ancona , Italy , Frederick was the son of the emperor Henry VI . He was known as the " puer Apuliae " ( son of Apulia ) . Some chronicles say that his mother , the forty - year - old Constance , gave birth to him in a public square in order to forestall any doubt about his origin . Frederick was baptised in Assisi . In 1196 at Frankfurt am Main the infant Frederick was elected King of the Germans . His rights in Germany were disputed by Henry ' s brother Philip of Swabia and Otto of Brunswick . At the death of his father in 1197 , Frederick was in Italy travelling towards Germany when the bad news reached his guardian , Conrad of Spoleto . Frederick was hastily brought back to his mother Constance in Palermo , Sicily , where he was crowned as King on 17 May 1198 , now Frederick I of Sicily , at only two years of age . Constance of Sicily was in her own right queen of Sicily , and she established herself as regent . In Frederick ' s name she dissolved Sicily ' s ties to Germany and the Empire that had been created by her marriage , sending home his German counsellors and renouncing his claims to the German throne and empire . Upon Constance ' s death in 1198 , Pope Innocent III succeeded as Frederick ' s guardian . Frederick ' s tutor during this period was Cencio , who would become Pope Honorius III . However , Markward of Annweiler , with the support of Henry ' s brother , Philip of Swabia , reclaimed the regency for himself and invaded the Kingdom of Naples . In 1200 , with the help of Genoese ships , he landed in Sicily and one year later seized the young Frederick . He thus ruled Sicily until 1202 , when he was succeeded by another German captain , William of Capparone , who kept Frederick under his control in the royal palace of Palermo until 1206 . Frederick was subsequently under tutor Walter of Palearia , until , in 1208 , he was declared of age . His first task was to reassert his power over Sicily and southern Italy , where local barons and adventurers had usurped most of the authority . Emperor . Otto of Brunswick had been crowned Holy Roman Emperor by Pope Innocent III in 1209 . In southern Italy , Otto became the champion of those noblemen and barons who feared Frederick ' s increasingly strong moves against them , exemplified by the firing of the pro - noble Walter of Palearia . The new emperor invaded Italy , where he reached Calabria without meeting much resistance . In response , Innocent sided against Otto , and in September 1211 at the Diet of Nuremberg Frederick was elected " in absentia " as German King by a rebellious faction backed by the pope . Innocent also excommunicated Otto , who was forced to return to Germany . Frederick sailed to Gaeta with a small following . He agreed with the pope on a future separation between the Sicilian and Imperial titles , and named his wife Constance as regent . Passing through Lombardy and Engadin , he reached Konstanz in September 1212 , preceding Otto by a few hours . Frederick was crowned as king on 9 December 1212 in Mainz . Frederick ' s authority in Germany remained tenuous , however , and he was recognized only in southern Germany ; in northern Germany , the center of Guelph power , Otto continued to hold the reins of royal and imperial power despite his excommunication . But Otto ' s decisive military defeat at the Bouvines forced him to withdraw to the Guelph hereditary lands where , virtually without supporters , he died in 1218 . The German princes , supported by Innocent III , again elected Frederick king of Germany in 1215 , and he was crowned king in Aachen on 23 July 1215 by one of the three German archbishops . It was not until another five years had passed , and only after further negotiations between Frederick , Innocent III , and Honorius III – who succeeded to the papacy after Innocent ' s death in 1216 – that Frederick was crowned Holy Roman Emperor in Rome by Honorius III , on 22 November 1220 . At the same time , Frederick ' s oldest son Henry took the title of King of the Romans . Unlike most Holy Roman emperors , Frederick spent few years in Germany . In 1218 , he helped Philip II of France and Eudes III , Duke of Burgundy to bring an end to the War of Succession in Champagne ( France ) by invading Lorraine , capturing and burning Nancy , capturing Theobald I , Duke of Lorraine and forcing him to withdraw his support from Erard of Brienne . After his coronation in 1220 , Frederick remained either in the Kingdom of Sicily or on Crusade until 1236 , when he made his last journey to Germany . He returned to Italy in 1237 and stayed there for the remaining thirteen years of his life , represented in Germany by his son Conrad . In the Kingdom of Sicily , he built on the reform of the laws begun at the Assizes of Ariano in 1140 by his grandfather Roger II . His initiative in this direction was visible as early as the Assizes of Capua ( 1220 , issued soon after his coronation in Rome ) but came to fruition in his promulgation of the Constitutions of Melfi ( 1231 , also known as " Liber Augustalis " ) , a collection of laws for his realm that was remarkable for its time and was a source of inspiration for a long time after . It made the Kingdom of Sicily an absolutist monarchy ; it also set a precedent for the primacy of written law . With relatively small modifications , the " Liber Augustalis " remained the basis of Sicilian law until 1819 . The Fifth Crusade and early policies in northern Italy . At the time he was elected King of the Romans , Frederick promised to go on crusade . He continually delayed , however , and , in spite of his renewal of this vow at his coronation as the King of Germany , he did not travel to Egypt with the armies of the Fifth Crusade in 1217 . He sent forces to Egypt under the command of Louis I , Duke of Bavaria , but constant expectation of his arrival caused papal legate Pelagius to reject Ayyubid sultan Al - Kamil ' s offer to restore the Latin Kingdom of Jerusalem to the crusaders in exchange for their withdrawal from Egypt and caused the Crusade to continually stall in anticipation of his ever - delayed arrival . The crusade ended in failure with the loss of Damietta in 1221 . Frederick was blamed by both Pope Honorius III and the general Christian populace for this calamitous defeat . In 1225 , after agreeing with Pope Honorius to launch a Crusade not after 1227 , Frederick summoned an imperial Diet at Cremona , the main pro - imperial city in Lombardy : the main arguments would be the struggle against heresy , the organization of the crusade and , above all , the restoration of the imperial power in northern Italy , which had been long usurped by the numerous communes there . These responded with the reformation of the Lombard League , which had already defeated his grandfather Frederick Barbarossa in the 12th century , and again Milan was chosen as the league ' s leader . The diet was cancelled , and the situation was set only through a compromise found by Honorius between Frederick and the League . During his sojourn in northern Italy , Frederick also invested the Teutonic Order with the territories in what would become East Prussia , starting what was later called the Northern Crusade . The Sixth Crusade . Problems of stability within the empire delayed Frederick ' s departure on crusade . It was not until 1225 , when , by proxy , Frederick had married Yolande of Jerusalem , heiress to the Kingdom of Jerusalem , that his departure seemed assured . Frederick immediately saw to it that his new father - in - law John of Brienne , the current king of Jerusalem , was dispossessed and his rights transferred to the emperor . In August 1227 , Frederick set out for the Holy Land from Brindisi , but was forced to return when he was struck down by an epidemic that had broken out . Even the master of the Teutonic Knights , Hermann of Salza , recommended that he return to the mainland to recuperate . On 29 September 1227 , Frederick was excommunicated by Pope Gregory IX for failing to honor his crusading pledge . Many contemporary chroniclers doubted the sincerity of Frederick ' s illness , and their attitude may be explained by their pro - papal leanings . Roger of Wendover , a chronicler of the time , wrote : Frederick eventually sailed again from Brindisi in June 1228 . The pope regarded that action as a provocation , since , as an excommunicate , Frederick was technically not capable of conducting a Crusade , and excommunicated the emperor a second time . Frederick reached Acre in September . Since all the local authorities denied him any help and most of the military orders denied him any help , and being the crusading army a meagre force , Frederick negotiated along the lines of a previous agreement he had intended to broker with the Ayyubid sultan , Al - Kamil . The treaty , signed in February 1229 , resulted in the restitution of Jerusalem , Nazareth , Bethlehem and a small coastal strip to the Kingdom of Jerusalem , though there are disagreements as to the extent of the territory returned . The treaty also stipulated that the Dome of the Rock and al - Aqsa Mosque were to remain under Muslim control and that the city of Jerusalem would remain without fortifications . Virtually all other crusaders , including the Templars and Hospitallers , condemned this deal as a political ploy on the part of Frederick to regain his kingdom while betraying the cause of the Crusaders . Al - Kamil , who was nervous about possible war with his relatives who ruled Syria and Mesopotamia , wished to avoid further trouble from the Christians , at least until his domestic rivals were subdued . The crusade ended in a truce and in Frederick ' s coronation as King of Jerusalem on 18 March 1229 , although this was technically improper . Frederick ' s wife Yolande , the heiress , had died , leaving their infant son Conrad as rightful king . There is also disagreement as to whether the ' coronation ' was a coronation at all , as a letter written by Frederick to Henry III of England suggests that the crown he placed on his own head was in fact the imperial crown of the Romans . In any case , Gerald of Lausanne , the Latin Patriarch of Jerusalem , did not attend the ceremony ; indeed , the next day the Bishop of Caesarea arrived to place the city under interdict on the patriarch ' s orders . Frederick ' s further attempts to rule over the Kingdom of Jerusalem were met by resistance on the part of the barons , led by John of Ibelin , Lord of Beirut . In the mid - 1230s , Frederick ' s viceroy was forced to leave Acre , and in 1244 , following a siege , Jerusalem itself was lost again to a new Muslim offensive . Whilst Frederick ' s seeming bloodless recovery of Jerusalem for the cross brought him great prestige in some European circles , his decision to complete the crusade while excommunicated provoked Church hostility . Although in 1230 the Pope lifted Frederick ' s excommunication at the Treaty of San Germano , this decision was taken for a variety of reasons related to the political situation in Europe . Of Frederick ' s crusade , Philip of Novara , a chronicler of the period , said " The emperor left Acre [ after the conclusion of the truce ] ; hated , cursed , and vilified . " Overall this crusade , arguably the first successful one since the First Crusade , was adversely affected by the manner in which Frederick carried out negotiations without the support of the church . He left behind a kingdom in the Levant torn between his agents and the local nobility , a civil war known as the War of the Lombards . The itinerant Joachimite preachers and many radical Franciscans , the Spirituals , supported Frederick . Against the interdict pronounced on his lands , the preachers condemned the Pope and continued to minister the sacraments and grant absolutions . Brother Arnold in Swabia proclaimed the Second Coming for 1260 , at which time Frederick would then confiscate the riches of Rome and distribute them among the poor , the " only true Christians " . The war against the Pope and Henry ' s revolt . During Frederick ' s stay in the Holy Land , his regent , Rainald of Spoleto , had attacked the Marche and the Duchy of Spoleto . Gregory IX recruited an army under John of Brienne and , in 1229 , invaded southern Italy . His troops overcame an initial resistance at Montecassino , and reached Apulia . Frederick arrived at Brindisi in June 1229 . He quickly recovered the lost territories and trialled the rebel barons , but avoided crossing the boundaries with the Papal States . The war was solved by the Treaty of San Germano in the summer of 1230 ; the emperor personally met Gregory IX at Anagni , making some concessions to the church in Sicily . He also issued the Constitutions of Melfi ( August 1231 ) , as an attempt to solve the political and administrative problems of the country , which had dramatically been shown by the recent war . While he may have temporarily made his peace with the pope , Frederick found the German princes another matter . Frederick ' s son Henry VII ( who was born 1211 in Sicily , son of Frederick ' s first wife Constance of Aragon ) had caused their discontent with an aggressive policy against their privileges . This forced Henry to a complete capitulation , and the " Statutum in favorem principum " ( " Statutes in favor of the princes " ) , issued at Worms , deprived the emperor of much of his sovereignty in Germany . Frederick summoned Henry to a meeting , which was held at Aquileia in 1232 . Henry confirmed his submission , but Frederick was anyway compelled to confirm the " Statutum " at Cividale soon afterwards . The situation for Frederick was problematic also in Lombardy , after all the emperor ' s attempts to restore the imperial authority in Lombardy with the help of Gregory IX ( at the time , ousted from Rome by a revolt ) turned to nothing in 1233 . In the meantime Henry in Germany had returned to an anti - princes policy , against his father ' s will : Frederick thus obtained his excommunication from Gregory IX ( July 1234 ) . Henry tried to muster an opposition in Germany and asked the Lombard cities to block the Alpine passes . In May 1235 , Frederick went to Germany , having no army with him : as soon as July , he was however able to force his son to renounce to the crown and all his lands , at Worms , and then imprisoned him . In Germany the Hohenstaufen and the Guelphs reconciled in the same year . Otto the Child , the grandson of Henry the Lion , deposed as Duke of Bavaria and Saxony in 1180 , conveyed the allodial Guelphic possessions to Frederick , who in return enfeoffed Otto with the same lands and additional former imperial possessions as the newly established Duke of Brunswick - Lüneburg , ending the unclear status of the German Guelphs , who were left without title and rank after 1180 . War in Lombardy . With peace north of the Alps , Frederick obtained by the German princes an army to suppress the rebel cities in Lombardy . Gregory tried to stop the invasion with diplomatic moves , but in vain . During his descent to Italy , Frederick had to divert his troops to quench a rebellion of Frederick II , Duke of Austria . At Vienna , in February 1237 , he obtained the title of King of the Romans for his 9 - year - old son Conrad . After the failure of the negotiations between the Lombard cities , the pope and the imperial diplomats , Frederick invaded Lombardy from Verona . In November 1237 he won the decisive battle in Cortenuova over the Lombard League . Frederick celebrated it with a triumph in Cremona in the manner of an ancient Roman emperor , with the captured " carroccio " ( later sent to the commune of Rome ) and an elephant . He rejected any suit for peace , even from Milan which had sent a great sum of money . This demand of total surrender spurred further resistance from Milan , Brescia , Bologna and Piacenza , and in October 1238 he was forced to raise the siege of Brescia , in the course of which his enemies had tried unsuccessfully to capture him . Frederick received the news of his excommunication by Gregory IX in the first months of 1239 while his court was in Padua . The emperor responded by expelling the Franciscans and the Dominicans from Lombardy , and electing his son Enzo as Imperial vicar for Northern Italy . Enzo soon annexed the Romagna , Marche and the Duchy of Spoleto , nominally part of the Papal States . The father announced he was to destroy the Republic of Venice , which had sent some ships against Sicily . In December of that year Frederick marched over Tuscany , entered triumphantly into Foligno and then in Viterbo , whence he aimed to finally conquer Rome , in order to restore the ancient splendours of the Empire . The siege , however , was ineffective , and Frederick returned to Southern Italy , sacking Benevento ( a papal possession ) . Peace negotiations came to nothing . In the meantime the Ghibelline city of Ferrara had fallen , and Frederick swept his way northwards capturing Ravenna and , after another long siege , Faenza . The people of Forlì ( which kept its Ghibelline stance even after the collapse of Hohenstaufen power ) offered their loyal support during the capture of the rival city : as a sign of gratitude , they were granted an augmentation of the communal coat - of - arms with the Hohenstaufen eagle , together with other privileges . This episode shows how the independent cities used the rivalry between Empire and Pope as a means to obtain maximum advantage for themselves . The Pope called a council , but Ghibelline Pisa thwarted it , capturing cardinals and prelates on a ship sailing from Genoa to Rome . Frederick thought that this time the way into Rome was opened , and he again directed his forces against the Pope , leaving behind him a ruined and burning Umbria . Frederick destroyed Grottaferrata preparing to invade Rome . Then , on 22 August 1241 , Gregory died . Frederick , showing that his war was not directed against the Church of Rome but against the Pope , drew back his troops and freed two cardinals from the jail of Capua . Nothing changed , however , in the relationship between Papacy and Empire , as Roman troops assaulted the Imperial garrison in Tivoli and the Emperor soon reached Rome . This back - and - forth situation was repeated again in 1242 and 1243 . Innocent IV . A new pope , Innocent IV , was elected on 25 June 1243 . He was a member of a noble Imperial family and had some relatives in Frederick ' s camp , so the Emperor was initially happy with his election . Innocent , however , was to become his fiercest enemy . Negotiations began in the summer of 1243 , but the situation changed as Viterbo rebelled , instigated by the intriguing local cardinal Ranieri Capocci . Frederick could not afford to lose his main stronghold near Rome , and besieged the city . Innocent convinced the rebels to sign a peace but , after Frederick withdrew his garrison , Ranieri nonetheless had them slaughtered on 13 November . Frederick was enraged . The new Pope was a master diplomat , and Frederick signed a peace treaty , which was soon broken . Innocent showed his true Guelph face , and , together with most of the Cardinals , fled via Genoese galleys to Liguria , arriving on 7 July . His aim was to reach Lyon , where a new council was being held since 24 June 1245 . Despite initially it seeming that the council could end with a compromise , the intervention of Ranieri , who had a series of insulting pamphlets published against Frederick ( in which , among other things , he defined the emperor as a heretic and an Antichrist ) , led the prelates towards a less accommodating solution . One month later , Innocent IV declared Frederick to be deposed as emperor , characterising him as a " friend of Babylon ' s sultan " , " of Saracen customs " , " provided with a harem guarded by eunuchs " like the schismatic emperor of Byzantium and , in sum , a " heretic " . The Pope backed Heinrich Raspe , landgrave of Thuringia as his rival for the imperial crown and set in motion a plot to kill Frederick and Enzo , with the support of his ( the pope ' s ) brother - in - law Orlando de Rossi , another friend of Frederick ' s . The plotters , however , were unmasked by the count of Caserta . The city of Altavilla , where they had found shelter , was razed , and the guilty were blinded , mutilated and burnt alive or hanged . An attempt to invade the Kingdom of Sicily , under the command of Ranieri , was halted at Spello by Marino of Eboli , Imperial vicar of Spoleto . Innocent also sent a flow of money to Germany to cut off Frederick ' s power at its source . The archbishops of Cologne and Mainz also declared Frederick deposed , and in May 1246 a new king was chosen in the person of Heinrich Raspe . On 5 August 1246 Heinrich , thanks to the Pope ' s money , managed to defeat an army of Conrad , son of Frederick , near Frankfurt . But Frederick strengthened his position in Southern Germany , acquiring the Duchy of Austria , whose duke had died without heirs , and one year later Heinrich died as well . The new anti - king was William II , Count of Holland . Between February and March 1247 Frederick settled the situation in Italy by means of the diet of Terni , naming his relatives or friends as vicars of the various lands . He married his son Manfred to the daughter of Amedeo di Savoia and secured the submission of the marquis of Monferrato . On his part , Innocent asked protection from the King of France , Louis IX ; but the king was a friend of the Emperor and believed in his desire for peace . A papal army under the command of Ottaviano degli Ubaldini never reached Lombardy , and the Emperor , accompanied by a massive army , held the next diet in Turin . The Battle of Parma and the End . An unexpected event was to change the situation dramatically . In June 1247 the important Lombard city of Parma expelled the Imperial functionaries and sided with the Guelphs . Enzo was not in the city and could do nothing more than ask for help from his father , who came back to lay siege to the rebels , together with his friend Ezzelino III da Romano , tyrant of Verona . The besieged languished as the Emperor waited for them to surrender from starvation . He had a wooden city , which he called " Vittoria " , built around the walls , where he kept his treasure and the harem and menagerie , and from where he could attend his favourite hunting expeditions . On 18 February 1248 , during one of these absences , the camp was suddenly assaulted and taken , and in the ensuing Battle of Parma the Imperial side was routed . Frederick lost the Imperial treasure and with it any hope of maintaining the impetus of his struggle against the rebellious communes and against the pope , who began plans for a crusade against Sicily . Frederick soon recovered and rebuilt an army , but this defeat encouraged resistance in many cities that could no longer bear the fiscal burden of his regime : Romagna , Marche and Spoleto were lost . In February 1249 Frederick fired his advisor and prime minister , the famous jurist and poet Pier delle Vigne , on charges of peculation and embezzlement . Some historians suggest that Pier was planning to betray the Emperor , who , according to Matthew of Paris , cried when he discovered the plot . Pier , blinded and in chains , died in Pisa , possibly by suicide . Even more shocking for Frederick was the capture of his son Enzo of Sardinia by the Bolognese at the Battle of Fossalta , in May of the same year . Only twenty - three at the time , he was held in a palace in Bologna , where he remained captive until his death in 1272 . Frederick lost another son , Richard of Chieti . The struggle continued : the Empire lost Como and Modena , but regained Ravenna . An army sent to invade the Kingdom of Sicily under the command of Cardinal Pietro Capocci was crushed in the Marche at the Battle of Cingoli in 1250 . In the first month of that year the indomitable Ranieri of Viterbo died and the Imperial " condottieri " again reconquered Romagna , Marche and Spoleto ; and Conrad , King of the Romans scored several victories in Germany against William of Holland . Frederick did not take part in of any of these campaigns . He had been ill and probably felt himself tired . Despite the betrayals and the setbacks he had faced in his last years , Frederick died peacefully , wearing the habit of a Cistercian monk , on 13 December 1250 in Castel Fiorentino ( territory of Torremaggiore ) , in Puglia , after an attack of dysentery . At the time of his death , his preeminent position in Europe was challenged but not lost : his testament left his legitimate son Conrad IV the Imperial and Sicilian crowns . Manfred received the principate of Taranto and the government of the Kingdom , Henry the Kingdom of Arles or that of Jerusalem , while the son of Henry VII was entrusted with the Duchy of Austria and the Marquisate of Styria . Frederick ' s will stipulated that all the lands he had taken from the Church were to be returned to it , all the prisoners freed , and the taxes reduced , provided this did not damage the Empire ' s prestige . However , upon Conrad ' s death a mere four years later , the Hohenstaufen dynasty fell from power and the Great Interregnum began , lasting until 1273 , one year after the last Hohenstaufen , Enzo , had died in his prison . During this time , a legend developed that Frederick was not truly dead but merely sleeping in the Kyffhäuser Mountains and would one day awaken to reestablish his empire . Over time , this legend largely transferred itself to his grandfather , Frederick I , also known as " Barbarossa " ( " Redbeard " ) . His sarcophagus ( made of red porphyry ) lies in the cathedral of Palermo beside those of his parents ( Henry VI and Constance ) as well as his grandfather , the Norman king Roger II of Sicily . A bust of Frederick sits in the Walhalla temple built by Ludwig I of Bavaria . Personality . His contemporaries called Frederick " stupor mundi " , the " wonder " – or , more precisely , the " astonishment " – " of the world " ; the majority of his contemporaries were indeed astonished – and sometimes repelled – by the pronounced unorthodoxy of the Hohenstaufen emperor and his temperamental stubbornness . Frederick II inherited German , Norman , and Sicilian blood , but by training , lifestyle , and temperament he was " most of all Sicilian . " Maehl concludes that " To the end of his life he remained above all a Sicilian " grand signore " , and his whole imperial policy aimed at expanding the Sicilian kingdom into Italy rather than the German kingdom southward . " Cantor concludes , " Frederick had no intention of giving up Naples and Sicily , which were the real strongholds of its power . He was , in fact , uninterested in Germany . " Frederick II was a religious skeptic . Despite the accusations of blasphemy and paganism , and the presence of Pagan and oriental elements in his imperial conceptions , Frederick remained substantially linked to traditional Christianism , as shown by his early contacts with both the Franciscans and the Cistercians ( in 1215 he was admitted in that order ' s praying community ) , as well as with St . Elizabeth . In spite of this , Frederick ' s religious skepticism was unusual for the era in which he lived , and to his contemporaries , highly shocking and scandalous , and his papal enemies used it against him at every turn ; he was subsequently defined " preambulus Antichrist " by the Pope Gregory IX , and , as Frederick allegedly did not respect the " privilegium potestatis " of the Church , he became excommunicated . In Palermo , where the three - year - old boy was brought after his mother ' s death , he was said to have grown up like a street youth . He was highly precocious . The only benefit from Innocent III ' s guardianship was that at fourteen years of age he married a twenty - five - year - old widow named Constance , the daughter of the king of Aragon . Both seem to have been happy with the arrangement , and Constance soon bore a son , Henry . At his coronation , he may have worn the red silk mantle that had been crafted during the reign of Roger II . It bore an Arabic inscription indicating that the robe dated from the year 528 in the Muslim calendar , and incorporated a generic benediction , wishing its wearer " vast prosperity , great generosity and high splendor , fame and magnificent endowments , and the fulfillment of his wishes and hopes . May his days and nights go in pleasure without end or change " . This coronation robe can be found today in the " Schatzkammer " of the Kunsthistorisches Museum in Vienna . Rather than exterminate the Arab - speaking population of Western Sicily , he deported them at Lucera . Not least , he enlisted them in his Christian army and even into his personal bodyguards . As Muslim soldiers , they had the advantage of immunity from papal excommunication . For these reasons , as well as his supposed Epicureanism , Frederick II is listed as a representative member of the sixth region of Dante ' s Inferno , The Heretics who are burned in tombs . A further example of how much Frederick differed from his contemporaries was the conduct of his Crusade in the Holy Land . Outside Jerusalem , with the power to take it , he parlayed five months with the Ayyubid Sultan of Egypt al - Kamil about the surrender of the city . The Sultan summoned him into Jerusalem and entertained him in the most lavish fashion . When the muezzin , out of consideration for Frederick , failed to make the morning call to prayer , the emperor declared : " I stayed overnight in Jerusalem , in order to overhear the prayer call of the Muslims and their worthy God " . The Saracens had a good opinion of him , so it was no surprise that after five months Jerusalem was handed over to him , taking advantage of the war difficulties of al - Kamil . The fact that this was regarded in the Arab as in the Christian world as high treason did not matter to him . When certain members of the Knights Templar wrote al - Kamil a letter and offered to destroy Frederick if he lent them aid , al - Kamil handed the letter over to Frederick . As the Patriarch of Jerusalem refused to crown him king , he set the crown on his own head . Science . Besides his great tolerance ( which , however , did not apply to Christian heretics ) , Frederick had an unlimited thirst for knowledge and learning . Frederick employed Jews from Sicily , who had immigrated there from the holy land , at his court to translate Greek and Arabic works . To the dislike of some of his contemporaries , Frederick did not believe things that could not be explained by reason . He forbade trials by ordeal in the firm conviction that in a duel the stronger would always win , whether or not he was guilty . Many of his laws continue to influence modern attitudes , such as his prohibition on physicians acting as their own pharmacists . This was a blow to the charlatanism under which physicians diagnosed dubious maladies in order to sell useless , even dangerous " cures " . Frederick II is the author of the first treatise on the subject of falconry , " De Arte Venandi cum Avibus " ( " The Art of Hunting with Birds " ) . In the words of the historian Charles Homer Haskins : Frederick ' s pride in his mastery of the art is illustrated by the story that , when he was ordered to become a subject of the Great Khan ( Batu ) and receive an office at the Khan ' s court , he remarked that he would make a good falconer , for he understood birds very well . He maintained up to fifty falconers at a time in his court , and in his letters he requested Arctic gyrfalcon s from Lübeck and even from Greenland . One of the two existing versions was modified by his son Manfred , also a keen falconer . Frederick loved exotic animals in general : his menagerie , with which he impressed the cold cities of Northern Italy and Europe , included hounds , giraffes , cheetahs , lynxes , leopards , exotic birds and an elephant . He was also alleged to have carried out a number of experiments on people . These experiments were recorded by the monk Salimbene di Adam ( who despised Frederick ) in his " Chronicles " . Amongst the experiments included shutting a prisoner up in a cask to see if the soul could be observed escaping though a hole in the cask when the prisoner died ; feeding two prisoners , sending one out to hunt and the other to bed and then having them disemboweled to see which had digested their meal better ; imprisoning children without any contact to see if they would develop a natural language . In the language deprivation experiment young infants were raised without human interaction in an attempt to determine if there was a natural language that they might demonstrate once their voices matured . It is claimed he was seeking to discover what language would have been imparted unto Adam and Eve by God . In his " Chronicles " Salimbene wrote that Frederick bade " foster - mothers and nurses to suckle and bathe and wash the children , but in no ways to prattle or speak with them ; for he would have learnt whether they would speak the Hebrew language ( which had been the first ) , or Greek , or Latin , or Arabic , or perchance the tongue of their parents of whom they had been born . But he laboured in vain , for the children could not live without clappings of the hands , and gestures , and gladness of countenance , and blandishments . " Frederick was also interested in the stars , and his court was host to many astrologers and astronomers , including Michael Scot and Guido Bonatti . He often sent letters to the leading scholars of the time ( not only in Europe ) asking for solutions to questions of science , mathematics and physics . In 1224 he founded the University of Naples , the world ' s oldest state university : now called Università Federico II , it remained the sole atheneum of Southern Italy for centuries . Appearance . A Damascene chronicler , Sibt ibn al - Jawzi , left a physical description of Frederick based on the testimony of those who had seen the emperor in person in Jerusalem : " The Emperor was covered with red hair , was bald and myopic . Had he been a slave , he would not have fetched 200 dirhams at market . " Frederick ' s eyes were described variously as blue , or " green like those of a serpent " . Law reforms . His 1241 Edict of Salerno ( sometimes called " Constitution of Salerno " ) made the first legally fixed separation of the occupations of physician and apothecary . Physicians were forbidden to double as pharmacists and the prices of various medicinal remedies were fixed . This became a model for regulation of the practice of pharmacy throughout Europe . He was not able to extend his legal reforms beyond Sicily to the Empire . In 1232 , he was forced by the German princes to promulgate the " Statutum in favorem principum " ( " statute in favor of princes " ) . It was a charter of liberties for the leading German princes at the expense of the lesser nobility and commoners . The princes gained whole power of jurisdiction , and the power to strike their own coins . The emperor lost his right to establish new cities , castles and mints over their territories . The " Statutum " severely weakened central authority in Germany . From 1232 the vassals of the emperor had a veto over imperial legislative decisions . Every new law established by the emperor had to be approved by the princes . Evaluation . Historians rate Frederick II as a highly significant European monarch of the Middle Ages . This reputation was present even in Frederick ' s era . Many modern medievalists reject the notion , sponsored by the popes , of Frederick as an anti - Christian . They argue that Frederick understood himself as a Christian monarch in the sense of a Byzantine emperor , thus as God ' s " viceroy " on earth . Whatever his personal feelings toward religion , certainly submission to the pope did not enter into the matter . This was in line with the Hohenstaufen " Kaiser - Idee " , the ideology claiming the Holy Roman Emperor to be the legitimate successor to the Roman Emperors . Twentieth - century treatments of Frederick vary from the sober ( Wolfgang Stürner ) to the dramatic ( Ernst Kantorowicz ) . However , all agree on Frederick II ' s significance as Holy Roman Emperor . In the judgment of British historian Geoffrey Barraclough , Frederick ' s extensive concessions to German princes — which he made in the hopes of securing his base for his Italian projects — undid the political power of his predecessors and postponed German unity for centuries . Family . Frederick left several children , legitimate and illegitimate : Legitimate issue . Frederick had a relationship with Bianca Lancia ( ca . 1200 / 10 - 1230 / 46 ) , possibly starting around 1225 . One source states that it lasted 20 years . She bore him three children : Matthew of Paris relates the story of a marriage " in articulo mortis " ( on her deathbed ) between them when Bianca was dying , but this marriage was never recognized by the Church . Nevertheless , Bianca ' s children were apparently regarded by Frederick as legitimate , evidenced by his daughter Constance ' s marriage to the Nicaen Emperor , and his own will , in which he appointed Manfred as Prince of Taranto and Regent of Sicily .