During Frederick’s absence, Gregory had devastated Apulia with fire and sword. His dead wife’s father, John de Brienne, the ex-king of Jerusalem, acted as captain of the papal mercenaries against him. On Frederick’s sudden reappearance, the papal troops were driven over the frontier and the Patrimony of St. Peter itself threatened by the victorious Emperor. Gregory found that his rashness had brought him into an impossible position, and was glad to accept the mediation which Hermann of Salza and Duke Leopold of Austria now proffered. [Sidenote: The Peace of San Germano, 1230.] On July 23, 1230, peace was made between Pope and Emperor at San Germano. In return for a promise to protect the Pope’s dominions and a confirmation of the papal rights over Sicily, Frederick was released from his excommunication. Soon after, Pope and Emperor met at Anagni with Hermann of Salza as the only witness of their conference. ‘The Pope,’ wrote Frederick, ‘has opened to me his heart, and has calmed my spirit. I will remember the past no longer.’ ‘The Emperor,’ wrote Gregory, ‘has come to seek me with the zeal of a devoted son, and has shown to me that he is ready to accomplish all my desires.’ Yet, despite these mutual protestations, the Treaty of San Germano so little went to the root of the matter that it was little more than a hollow truce. Both sides still watched each other with jealous suspicion. However, the truce was kept for several years, since neither Pope nor Emperor was ready to strike the decisive blow for power. Frederick devoted the period succeeding the Treaty of San Germano to the building up of his Southern despotism. His policy now became more exclusively Italian. With the hope of getting help from the German princes in carrying out his Southern schemes, he recklessly played into their hands, and wantonly destroyed the well-ordered authority over his Northern kingdom that he had inherited from his father and grandfather. [Sidenote: Contrast between Frederick’s Italian and German policy.] His German and Sicilian policies stand in the strongest contrast. While he trampled down all feudal communities in the Norman kingdom in favour of a centralised bureaucracy dependent upon himself, he threw to the winds every monarchical and national tradition in Germany. There was something of the wilfulness that is so characteristic of him in this strangely twofold and contradictory action. It strikes at the very root of Frederick’s claims to the higher statesmanship. Their only reconciliation is the fact that the Emperor’s policy was but the policy of the moment. So long as he could crush his papal enemy, he was utterly careless of the general tendency of his work. The ruin of the Hohenstaufen was already prepared for when Frederick bartered his German kingship for an immediate triumph over his hated foe. It was all the more certain, since the elaborate edifice that he imagined he was building up in Italy was but a house erected on the sand.