http://en.wikipedia.org/wiki/Frederick_II,_Holy_Roman_Emperor
Frederick II (December 26, 1194 – December 13, 1250), Holy Roman Emperor of the Hohenstaufen dynasty, was pretender to the title of King of the Romans from 1212, unopposed holder of that monarchy from 1215, and Holy Roman Emperor from 1220 until his death in 1250. He was also King of Sicily, from 1198 to 1250, where he was raised and lived most of his life (his mother, Constance of Sicily, was the daughter of Roger II of Sicily). He is also referred to as Frederick I of Sicily. His empire was frequently at war with the Papal States, so it is not surprising that he was excommunicated twice. Pope Gregory IX went so far as to call him the anti-Christ. After his death the idea of his second coming where he would rule a 1000-year reich took hold, possibly in part because of this.
Said to speak nine languages and be literate in seven [Armstrong 2001, p. 415] (at a time when many monarchs and nobles were not literate at all), Frederick was a very modern ruler for his times, being a patron of science and learning (astronomy and astrology, also: one of his advisors was the famous astrologer Guido Bonatti from Forlì) and having fairly advanced views on economics. He abolished state monopolies, internal tolls, and import regulations within his empire.
He was patron of the Sicilian School of poetry, where in his royal court in Palermo, from around 1220 to his death, we witness the first use of a literary form of an Italo-Romance language, Sicilian. The poetry that emanated from the school predates the use of the Tuscan idiom as the preferred lingua franca of the Italian peninsula by at least a century. The school and its poetry were well known to Dante and his peers and had a significant influence on the literary form of what was eventually to become the modern Italian.
He was known in his own time as the Stupor mundi ("wonder of the world"). Frederick wrote, or rewrote, a manual on the art of falconry, De arte venandi cum avibus ("On the art of hunting with birds"), of which many illustrated copies survive from the 13th and 14th centuries.
Born in Jesi, near Ancona, Frederick was the son of the emperor Henry VI. Some old chronicles say he was born in a public square of the city of Jesi, in northern Italy, while his father was entering triumphantly into Palermo. Frederick was baptised in Assisi.
In 1196 at Frankfurt am Main the child Frederick had already been elected to become King of the Germans. At the death of his father in 1197, the two-year-old Frederick was in Italy in voyage towards Germany, and when the bad news reached his guardian, Conrad of Spoleto, he was hastily brought back to Palermo to Constance. It was a good move, as Henry's empire dissolved, and its monarchy was disputed by Henry's brother Philip of Swabia and Otto IV.
His mother, Constance of Sicily, had been in her own right queen of Sicily; she had Frederick crowned King of Sicily and established herself as regent. In Frederick's name she dissolved Sicily's ties to the Empire, sending home his German counsellors (notably Markward of Anweiler and Gualtiero da Pagliara), and renouncing his claims to the German kingship and empire.
Upon Constance's death in 1198, Pope Innocent III succeeded as Frederick's guardian until he was of age: he was crowned King of Sicily on May 17, 1198, being only three years of age, and received some of his early formal education in Rome. He was to remember forever, however, the time spent in his early years in the court of Palermo, where Arab, German, Latin, Byzantine, Norman, Provencal and even Jewish influences combined.
Otto of Brunswick had been crowned Holy Roman Emperor by Pope Innocent III in 1209. In September 1211 at the Diet of Nuremberg Frederick was elected in absentia as German King by a rebellious faction backed by Innocent, who had fallen out with Otto and excommunicated him; he was again elected in 1212 and crowned December 9, 1212 in Mainz; yet another coronation ceremony took place in 1215. Being King of the Germans had been the traditional precursor step for emperorship. However, until the debacle at the Battle of Bouvines in 1214, Frederick's authority was quite tenuous 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 excommunication.
Otto's decisive military loss at Bouvines lost him the practical means to hold onto kingship and emperorship, and he withdrew to the Guelph hereditary lands to die, virtually without supporters, in 1218. (See also Guelphs and Ghibellines). The German princes, supported by Innocent III, again elected Frederick king of Germany in 1215, and the pope crowned him king in Aachen on July 23, 1215. 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 November 22, 1220. At the same time his oldest son Henry took the title of King of the Romans.
Unlike most Holy Roman emperors, Frederick spent little of his life in Germany. After his coronation in 1220, he remained either in the Kingdom of Sicily or on Crusade until 1236, when he made his last journey to Germany. (At this time, the Kingdom of Sicily, with its capital at Palermo, extended onto the Italian mainland to include most of southern Italy.) He returned to Italy in 1237 and stayed there for the remaining 13 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) 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, the first centralized state in Europe to emerge from feudalism; 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.
During this period, he also built the Castel del Monte and in 1224 created the University of Naples: now called Università Federico II, it remained the sole atheneum of Southern Italy for centuries. After the death of the last Duke of Zähringen, Frederick explicitly or implicitly granted the status of Imperial Free City to Berne. The corresponding Golden Charter of Bern of 1218, though, has now come to be regarded as a forgery. In 1224 Frederick II confirmed the inhabitants of Terra Prussia Prussian Land, etc as Reichsfreie under authority of the emperor, the empire and the church only and exempted them from service to or jurisdiction of any local dukes. Later in 1224 the pope authorized bishop William of Modena as Legate in Prussia etc. In 1226 he elevated Lübeck to an Imperial Free City.
In 1226, by means of the Golden Bull of Rimini he confirmed the legitimacy of rule by the Teutonic Knights under their headmaster Hermann von Salza over the Prussian lands east of the Vistula including Prussian Culmerland (Chelmno Land).
At the time he was crowned Emperor, Frederick had promised to go on crusade. In preparation for his crusade, Frederick had, in 1225, married Yolande of Jerusalem, heiress to the Kingdom of Jerusalem, and immediately taken steps to take control of the Kingdom from his new father-in-law, John of Brienne. However, he continued to take his time in setting off, and in 1227, Frederick was excommunicated by Pope Gregory IX for failing to honor his crusading pledge - perhaps unfairly, at this point, as his plans had been delayed by an epidemic. Frederick himself had fallen ill as a result of this epidemic, this being the main reason for his delay. Many contemporary chroniclers doubted the sincerity of Frederick's illness, stating that he had deliberately delayed for selfish resons, and this attitude can in part be explained by their pro papal stance. Roger of Wendover, a chronicler of the time, wrote ‘he went to the Mediterranean sea, and embarked with a small retinue; but after pretending to make for the holy land for three days, he said that he was seized with a sudden illness…this conduct of the emperor redounded much to his disgrace, and to the injury of the whole business of the crusade,’(‘Roger of Wendover’, Christian Society and the Crusades, ed Peters (Philadelphia 1971).
He eventually embarked on the crusade the following year (1228), which was seen on by the pope as a rude provocation, since the church could not take any part in the honor for the crusade, resulting in a second excommunication. Frederick did not attempt to take Jerusalem by force of arms. Instead, he negotiated restitution of Jerusalem, Nazareth, and Bethlehem to the Kingdom with sultan Al-Kamil, the Ayyubid ruler of the region, who was nervous about possible war with his relatives who ruled Syria and Mesopotamia and wished to avoid further trouble from the Christians. The crusade ended in a truce and in Frederick's coronation as King of Jerusalem on March 18, 1229 — although this was technically improper, as Frederick's wife Yolande, the heiress, had died in the meantime, leaving their infant son Conrad as rightful heir to the kingdom. 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. By the mid-1230s, Frederick's viceroy had been forced to leave Acre, the capital, and by 1244, Jerusalem itself had been lost again to a new Muslim offensive.
Whilst Frederick's seeming bloodless victory in recovering Jerusalem for the cross brought him great prestige in some European circles, his decision to complete the crusade whilst excommunicate raised hostility from Church circles. Although in 1231 the pope rescinded Frederick's excommunication at the Peace of San Germano, this decision was taken for a variety of reasons also 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." (The History of Philip of Novara, Christian Society and the Crusades, ed Peters. Philadelphia, 1971). Overall the success of this crusade, the first successful one after the failures of the fourth and fifth crusades, was adversely affected by the manner in which Frederick carried out negotiations without the support of the church.

The war against the Pope and the Italian Guelphs:
While he may have temporarily made his peace with the pope, the lesser German princes were another matter. In 1231, Frederick's son Henry (who was born 1211 in Sicily, son of Frederick's first wife Constance of Aragon) claimed the crown for himself and allied with the Lombard League. The rebellion failed, though not utterly; Henry was imprisoned in 1235, and replaced in his royal title by his brother Conrad, already the King of Jerusalem; Frederick won a decisive battle in Cortenuova over the Lombard League in 1237.
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 Padova. The emperor replied expelling the Minorites and the preachers from Lombardy, and electing his son Enzio as Imperial vicar for Northern Italy. Enzio 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 Toscana, 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 vain, 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 mean to obtain the maximum advantage for themselves.
The Pope had 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 again directed his forces against the Pope, trailing behind him a ruined and burning Umbria. Frederick destroyed Grottaferrata preparing to invade Rome. But on August 22, 1240, 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 repeated again in 1242 and 1243. Though unfruitful, these expeditions around Rome permitted Frederick to capture treasures from the church of the cities he passed through, and gave him the opportunity to enjoy the pleasant nature of hills, lakes and woods of the Latium.

His last and fiercest opponent, Innocent IV:
A new pope, Innocent, was elected on June 25, 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 instead was to become his fiercest enemy. Negotiations began in the summer of 1243, but the situation changed as Viterbo rebelled, instigated by the intriguing Cardinal Ranieri of Viterbo. Frederick could not lose his main stronghold near Rome, and besieged the city. Many authorities state that the Emperor's star began its descent with this move. Innocent convinced him to withdraw his troops, but Ranieri nonetheless had the Imperial garrison slaughtered on November 13. Frederick was full of powerless rage. 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 the Ligurian republic, arriving on July 7. His aim was to reach Lyon, where a new coucil was held beginning June 24, 1245.
One month later, Innocent IV declared Frederick to be deposed as emperor: he was characterized 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 Enzio, with the support of his (the pope's) brother-in-law Orlando de Rossi, who was a friend of Frederick's as well.
The conjurers, however, were unmasked by the count of Caserta. The vengeance was terrible: the city of Altavilla, where they had found shelter, was razed, and the guilty were blinded, mutilated and burnt alive or hung. 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.

Frederick II's troops paid with leather coins, from Chigi Codex, Vatican Library
Innocent also sent a flow of money to Germany to cut off Frederick's power at its source. The archbishops of Köln and Mainz also declared Frederick deposed, and in May 1246 a new king was chosen in the person of Heinrich Raspe. On August 5 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 titular 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. Marrying his son Manfred to the daughter of Amedeo di Savoia and securing the submission of the marquis of Monferrato, Frederick also gained control of the passages of the Eastern Alps, clearing the route to Lyon, where he hoped finally to settle the long-standing dispute with the Pope.
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.
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. Enzio 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 the besieged surrendered of starvation. He had a true wooden city built around the walls, pompously called Vittoria ("Victory").
Here Frederick kept the treasure with the harem and the menagerie, and from its pavilions he could attend his favorite hunting expeditions. On February 18, 1248, during one of these absences the camp was suddenly assaulted and conquered, and in the ensuing Battle of Parma the Imperial side was routed. Frederick lost the Imperial treasure and, with it, any hope to keep up his struggle against the rebellious communes, as well as the triumphant Pope, who began plans for a crusade against Sicily. Though he soon recovered and rebuilt an army, this defeat spurred the rebellious feeling of many cities that could no longer bear his fiscal and monarchic regime: Romagna, Marche and Spoleto were lost.
On February 1249 Frederick, who had just lost his other faithful minister Taddeo of Suessa, fired his advisor and prime minister, the famous jurist and poet Pier delle Vigne. The charge was speculation and embezzlement. Some historians, however, maintain instead that Pier was planning to betray the Emperor: according to Matthew of Paris, he cried when he discovered the betrayal. Pier, blinded and in chains, died in Pisa, presumably by suicide (a presumption that placed him in the Seventh Circle of Dante's Hell in Canto XII of Inferno). Even more shocking for Frederick was the capture of his son Enzio by the Bolognese at the Battle of Fossalta, in the May of the same year. Only 23 at the time, he was thrown into a jail cell in which he was to spend the rest of his life, dying in 1272. The place of the king of Sardinia was taken over by the marquis Oberto Pallavicino, a skilled but cruel man, not different from his ill-famed contemporary Ezzelino. In this period Frederick lost another son, Richard of Chieti. But the struggle continued: the Empire lost Como and Modena, but regained Ravenna and another 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.
The sarcophagus of Frederick II of Hohenstaufen in the Cathedral of Palermo.
Frederick did not take part of any of these campaigns. He had been ill and probably felt himself tired. Despite the betrayals and the ill happenings he had faced in his last years, Frederick died peacefully on December 13, 1250 in Castel Fiorentino near Lucera, in Puglia, after an attack of dysentery: in his last moment he wore the habit of a Cistercian monk. 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 the Duchy of Austria and the Marquisate of Styria. His will was 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 not damaged the Empire's pride.
However, upon Conrad's death a mere four years later, the Hohenstaufen dynasty fell from power and an interregnum began, lasting until 1273, one year after the last Hohenstaufen, Enzio, had died in his prison. During this time, a legend developed that Frederick was not truly dead, but merely slept in the Kyffhaeuser 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.