Previous emperors had been figureheads; Frederick became the real ruler of Europe. The kings of Denmark and Poland fully acknowledged themselves his vassals. So also, though less definitely, did the King of England. For a moment the imperial unity of Europe seemed reviving. Only one of the Emperor’s great dukes, Henry the Lion, of Saxony, dared stand against him; and Henry was ultimately crushed. The war-cries of the two opponents, however, became eternalized as factional names in the struggle of Frederick’s successors against other foes. For generations whoever upheld the empire was a Waibling, and whoever would attack it, on whatsoever plea, a Welf. Frederick, having established his power in Germany, attempted to assert it in Italy as well; and so the strife passed over the Alps and became that of Ghibelline against Guelf, in Italian phrase, of emperor against pope, of monarchy against democracy.
It was this fatal insistence upon Italian authority that brought disaster upon Frederick and all his house, and ultimately upon the empire as well, and on the entire German race. The Italians had been quite content to call themselves subjects of a Holy Roman Empire which extended but vaguely over Europe, and whose chief took his title from their ancient city and only came among them to be crowned. They looked at the matter in a wholly different light when Frederick regarded his position seriously, and interfered in their affairs with the strong hand, crushing their feuds and exacting money tribute. Rebellion was promptly kindled, and for twenty years one German army after another dwindled away in the passage of the Alps, wasted under the fevers of Italian marshes, or was crushed in desperate battle. By the treaty of Constance, in 1183, Frederick confessed the one defeat of his career. He acknowledged the practical independence of the Italian cities.
The Emperor had in fact encountered a power too strong for him. He had been struggling against the beginnings of modern democracy, a system stronger even in its infancy than the ancient rule of the aristocracy which it has gradually supplanted. The resistance of Italy came not from its knights and lords, but from its great cities, which had been slowly growing more and more self-reliant and independent. The rise of these city republics of the Middle Ages cannot be fully traced. Everywhere little communities of men seem to have been driven by desperation to build walls about their group of homes and to defy all comers. As it was in Italy that the ancient Roman civilization had been most firmly established and the barbarian dominance least complete, so it was in Italy that these walled towns first asserted their importance. Venice indeed, protected by her marshes, we have seen establishing a somewhat republican form even from her foundation. She and Genoa and Pisa defended themselves against the