Such a crime could not go unpunished, and Frederic, at the head of a powerful army, crossed the Alps and appeared, when least expected, in the plains of Lombardy. Meanwhile the Milanese were putting into execution their perfidious designs against Como and Lodi, and offered to the Emperor the sum, enormous for that age, of four hundred gold marks, on condition that he would recognize their sovereignty over these cities.
But the proposition was indignantly rejected. "Wretches," said he to the Milanese ambassadors, "do you presume to bribe me to palliate your treachery? Do you propose to the Emperor of Germany to become a partner in your baseness? Even were it in my power to sell the half of my domains, I would rather turn your city into a paltry village than countenance this exercise of arbitrary despotism over a country which has as much right to liberty as yourselves." The result of the interview was a solemn engagement, on the part of the Milanese, to indemnify Lodi and Como for all damages sustained, as the powerful alliances of Milan, her military strength, and the comparative weakness of the German army, did not, at the time, permit of the absolute subjection of Lombardy.
Thence Frederic marched towards Tortona, an ally of the Milanese, which had attacked and ravaged the territory of Pavia. Explanations were demanded, but, confiding in the strength of its fortifications, Tortona haughtily refused. The Emperor at once attacked the town, stormed the works, and reduced it to ashes.
This terrible example dismayed the Milanese, who were ignorant of the fate in store for them, but they had learned to appreciate the energy and courage of the Emperor, and they began to estimate the necessity of strengthening and renewing the alliances which had formerly existed between them and the neighboring States.
Scarcely had the Emperor recrossed the Alps, and received the crown from the hands of Pope Adrian IV., when the Milanese resumed their depredations upon Lodi. Far from making amends for their former damages, and thus fulfilling the stipulations of the treaty, they marched a powerful army against the city, imprisoned or killed the inhabitants, and only retired after laying waste the vineyards, and destroying the crops throughout the entire province.
Again the inhabitants of Lodi sought the assistance of the Emperor.
Barbarossa was incensed beyond measure at this insolent disregard, not only of his threats, but even of his Imperial supremacy. Such audacity demanded prompt repression, and Imperial edicts were at once issued to all the spiritual and temporal princes of the Empire, summoning them to join the Army destined to operate in Italy.
In the month of June, 1158, the German army crossed the Alps, and Milan was besieged and taken after a heroic defence.
Again Frederic, either through pity or a desire to spare the noble city, or through the temptation of a costly bribe, delayed the execution of his threats, although urgently counselled to inflict upon Milan the fate of Tortona. But he humbled the pride of the haughty Lombards: all their rights and privileges were confiscated, and they were compelled to rebuild Lodi and Como, while all duties and customs were henceforth to revert to the Imperial treasury; a fine of nine thousand silver marks was imposed, and as a guarantee for the fulfilment of these and many other conditions, three hundred of the principal citizens were to be given up and held as hostages.
The Emperor then disbanded the greater portion of his German levies, and convoked a Diet of the princes, prelates, counts, and chief civil dignitaries, who in general assembly were to attend to the pacification of Italy, and the re-establishment of order, and to define precisely the respective rights of the sovereign and his subjects.