anticipated effect of quelling the insurrection; Henry was sent a prisoner to Italy and disappeared from history. Then, in August 1235, amid surroundings of great splendour, the emperor held a diet at Mainz, which was attended by a large number of princes. This diet is very important in the legal history of Germany, because here was issued that great "land peace" (_Landfrieden_) which became the model for all subsequent enactments of the kind. By it private war was declared unlawful, except in cases where justice could not be obtained; a chief justiciar was appointed for the Empire; all tolls and mints erected since the death of Henry VI. were to be removed; and other provisions dealt with the maintenance of order. Frederick in Germany. In 1236, during another short stay in Germany, Frederick in person led the imperial army against Frederick II., duke of Austria, who had defied and overcome his representatives; having taken possession of Vienna and the Austrian duchies he there secured the election of his son Conrad, who had already succeeded his brother as duke of Swabia, as king of the Romans (May 1237). But in spite of these imposing displays of power the princes looked with suspicion upon an emperor who was almost a stranger to their country and who was believed to be a renegade from their faith, and soon after Frederick's return to Italy the gulf between him and his German subjects was widened by his indifference to a great danger which threatened them. This came from the Mongols who ravaged the eastern frontiers of the country, but the peril was warded off by the efforts of Henry II., duke of Silesia, who lost his life in a fight against these foes near Liegnitz in April 1241, and of Wenceslaus I., king of Bohemia. Frederick and the pope.