the Guelfs, as Duke of the new duchy of Brunswick (see also page 331). Frederick’s friendship with the Guelfs, following closely upon his alliance with England, clearly marks his departure from his ancestors’ policy. Even the towns were conciliated by the renewal of their privileges. Only the Duke of Austria, the brother-in-law of Henry VII., still remained unappeased. He was proscribed in the diet of 1236 and his territories invaded. But the Duke resisted so vigorously that Frederick, who had before this returned to Italy, was forced once more to cross the Alps. Early in 1237 the Emperor entered Vienna in triumph, though even after this the stubborn duke held his own, and when peace was at last made in 1239, he secured the full restitution of his estates. [Sidenote: Conrad, King of the Romans, 1237.] Frederick took with him to Vienna Conrad, his son by Isabella of Brienne, then a boy of nine. The assembled princes declared that the little Conrad was to be preferred to Henry, as David had been put in the place of Saul. He was elected King of the Romans, and on Frederick’s speedy return to Italy, the government of Germany was, for a second time, carried on in the name of a boy-king. The troubles that had disturbed the reign of Henry were now quickly renewed. Notwithstanding the rapid diminution of the royal power, the age of Frederick II. is one of no small moment in the development of German civilisation, though little of the credit for it can be set down to the absentee and incurious Emperor. But in truth the removal of the imperial authority was not all loss. [Sidenote: German Civilisation under Frederick II.] It had never been sufficient of a reality to secure for all Germany permanent peace, and even in the days of the strongest of German kings much of the merit of upholding order and civilisation had belonged to the local potentates. Their complete recognition and the full legalisation of their power now substituted a large number of small local centres of authority for the one unifying power of the old German king. German unity suffered, but national unity was a far-off ideal in Northern Europe in the thirteenth century. The great development of trade, wealth, law, literature, and civilisation showed that Germany was far from being an absolute loser by the change of system. Unluckily the power of these lesser rulers did not, as in France, prepare the way for a strong monarchy when the time grew ripe for a single government. Germany paid the penalty for her premature unity under her early kings by her inability to set up a national authority when national states became possible. [Sidenote: Commerce and the Towns.]