The princes, therefore, especially the ecclesiastics, were the pivot on which Frederick II set his government in Germany, giving full development to a political system, whose roots were in the reign of his ancestor. In this way he achieved the goal which he aimed above all: to have full freedom of action in Italy. Germany had its sovereign for ten years in all of its fifty or so of reign, and also in two stages: from 1212 to 1220, and from 1235 to 1237. However, apart from the decisive easing of central power, the system ensured the internal peace, and also withstood the tests of the emperor’s struggle with the papacy long enough. Especially during the regency of Engelbert of the counts of Berg, archbishop of Cologne (1220-1225), who resorted to the expedient of the Landfrieden, the country experienced a period of relative tranquility. This was less with the regency of Ludwig I of Wittelsbach, Duke of Bavaria (1225-1228), who preferred direct interventions in local disputes, and also attempted an ephemeral rebellion (1229), which however was the only disturbance of a certain importance in Germany.
Things began to change when (1229) the son of Frederick II, Henry, became regent from 1217 duke of Swabia, from 1220 rector of Burgundy and king of the Romans (Frankfurt, April). The young man (he was 17 years old) began with imprudent arrogance to oppose his father’s political directives, favoring cities, ministeriales and lesser nobility, the classes with interests opposite to those of the principles on which the emperor based his system. After having made an act of submission to Aquileia (1232), Henry took an increasingly rebellious attitude, not only not supporting with the fervor, which was in his father’s will, the ferocious persecution conducted by the princes against the heretics in 1232-1234, but seeking to alienate the king of France, Louis IX, from Frederick II, until he made himself openly rebellious by allying himself with the Italian cities with which the emperor was struggling (December 1234). The German cities, however, remained faithful, and among the princes only Frederick II, Duke of Austria, the last of the Babenbergs, was inclined to rebel. The energetic action of the emperor, who immediately rushed to Germany, cut off the movement in the bud. Enrico, humiliated at Wimpfen on the Neckar, after the diet of Worms in July 1235 he was taken prisoner to Italy, where he died in 1242. Considerable political importance for the position of the Hohenstaufen in the lower Rhine region, of which we already noted the close relations with England, were the wedding celebrated in Worms, on the occasion of the diet, by Frederick II with Isabella, sister of that king (15 July 1235). The following month there was also the final reconciliation of the Guelphs with the Swabians on the diet of Mainz. From 1214 the Guelph branch of the Palatine counts of the Rhine had died out, which Frederick had made over from the Wittelsbachs of Bavaria, who, with the union of the Rhine Palatinate to their duchy, had achieved a notable increase in power. The male offspring of the Guelphs remained represented by Otto of Brünswick, grandson of Emperor Otto IV. At the time of the excommunication launched on Frederick II, he had declined the offer made to him by the pope of the imperial crown, avoiding the rekindling of a fight between Guelphs and Ghibellines. In Mainz he got the reward. Frederick II gave him the fief of Brünswick-Lüneburg, with wide privileges, and with the ducal title. There followed the punishment of the Duke of Austria, banned by the Empire. In January 1237 the same emperor was in Vienna, which he declared an imperial city, while he placed Styria under direct dependence on the Empire and reserved the same with Austria. In Vienna (February) the princes elected Frederick II’s other son, Conrad, who was nine years old at the time, king over the Romans, and whose election they later confirmed in Speyer (July 1237).
According to Medicinelearners, the King of Bohemia and the Duke of Bavaria, although charged with the execution of the ban, did nothing to oppose the Babenberg. It was the first sign of the storm that would once again drag Germany into full anarchy. A pact was made between the three princes, which manifested itself in open revolt after Gregory IX had again struck the emperor with excommunication (20-24 March 1239). Siegfried, archbishop of Mainz, archchancellor and procurator of the Empire in Germany, isolated the motion, keeping the Margravîs of Thuringia and Misnia from taking part. The high clergy also generally remained faithful. In the same year the king of Bohemia and the Babenberg returned to obedience, the latter earning their reinstatement in the duchy. But the emperor’s prestige suffered a serious blow when, threatened by the Mongols, Germany did not rush to defend it from Italy. The Mongols, disheartened by the desperate resistance against which they had struck at the Austrian and Bohemian borders, and then in Silesia, although in Liegnitz (9 April 1241) they had won that Duke Henry, who fell on the field like a hero with most of his men, and shaken by the news of the situation in Asia due to the death of their great khan Ogotai, they returned to the East. The threat was gone. But in the meantime it is certain that Frederick II had given the feeling of having failed in his duty as a German sovereign. On the other hand, the bitterness assumed by the struggle between the Hohenstaufen and the papacy was now such that it could not fail to shake the fidelity of the high German clergy. Already in 1241 the archbishop of Mainz himself abandoned the imperial party, and together with the other two Rhenish archbishops, of Trier and Cologne, he became the center of the anti-Swabian movement in Germany.