The Europe of 1400 was confronted by an Eastern question of supreme urgency: that of repulsing the Turks who had just taken Adrianople and wiped out the Serbian kingdom. The imminent danger ought to have concentrated all efforts on the Balkans. Yet the imperative task of European politics does not yet disengage itself from the old idea of the crusades. People only succeeded in seeing the Turkish question as a secondary part of the sacred duty in which their ancestors had failed: the conquest of Jerusalem.
