England, by her failure, was reduced for a while to a secondary rank
among the nations, the purely German Empire of the fifteenth century was
still the leading power east of the Rhine. This was partly the result of
calamities to neighbouring nations which could neither be foreseen or
obviated. While Western Europe was shielded, in the later Middle Ages,
from the inroads of alien races, Eastern Europe felt the impact of the
last migratory movements emanating from Central Asia and the Moslem
lands. In the thirteenth century the advance guards of the Mongol Empire
destroyed the medieval kingdom of Poland, and reduced the Russian
princes to dependence upon the rulers of the Golden Horde. In the
fifteenth, the advance of the Turks along the Danube completed the ruin
of the Magyar state, already weakened by the feuds of aristocratic
factions. But, apart from these favourable circumstances, the resources
of Germany were irresistible when they could be concentrated. Twice
after the Great Interregnum the integrity of the Empire was threatened
by the Bohemian kingdom. On the first occasion, when Ottocar II had
extended his power into the German lands between Bohemia and the
Adriatic, he was overthrown by Rudolf of Hapsburg at the battle of the
Marchfeld (1278); and a new Hapsburg principality was formed out of the
reconquered lands to guard the south-east frontier against future
incursions of Czech or Magyar. On the second, when the Hussite levies
carried their devastations and their propaganda into all the
neighbouring provinces of the Empire (1424-1434), crusade after crusade
was launched against Bohemia until the heretics, uniformly victorious in
the field, were worn out by the strain of their exertions against
superior numbers, and all the more moderate spirits recognised that such
triumphs must end in the ruin and depopulation of Bohemia. The case was
the same in the Baltic, where the struggle with Danish ambitions was
left to the princes and the free towns. Waldemar II (1202-1241), who had
planned to revive the Scandinavian Empire of the great Canute, the