There is no doubt that the Greek emperors stood in great need of succour from the Latins, but this pusillanimous policy, which unceasingly invoked the assistance of other nations, only proclaimed the weakness of the empire, and necessarily deprived the Greeks, in the hour of peril, of all confidence in their own strength. On the other side, these cries of alarm, which constantly resounded throughout Europe, met with nothing but incredulous minds and indifferent hearts. It was in vain that the warriors of the West heard it for ever repeated that Constantinople was the barrier of Christendom; they could not consider a city which was unable to provide for its own defence, and was always in want of succour, as a barrier capable of arresting the course of a powerful enemy. When Gregory XI. solicited the emperor of Germany to assist Constantinople, that prince replied sharply that the Greeks had opened the gates of Europe to the Turks, and _let the wolf into the sheep-fold_. At this time the miserable remains of the empire of the Cæsars was comprised within the extent of less than twenty leagues, and in this narrow space there was an empire of Byzantium, and an empire of Rodesto or Selivrea; the princes, whom ties of blood ought to have united, quarrelled with inveterate fury for the rags of the imperial purple. Brother was armed against brother, and father and son declared open war; all the crimes that had formerly been inspired by the ambition of obtaining the sceptre of the Roman world, were still committed for the advantage of reigning over a few miserable cities. Such was the empire of the East, upon which the Ottoman dominions continued on all sides to encroach. At the period of which we are speaking, all the princes of the family of Palæologus having been commanded to repair to the court of Bajazet, obeyed his supreme order tremblingly; and if they came out safe and sound from the palace of the sultan, which was for them the den of the lion, it was because pity disarmed the executioner, and because the contempt they inspired among the Mussulmans was their safeguard. The Ottoman emperor contented himself with commanding Manuel, the son and successor of John Palæologus, not to deliver Constantinople up to him, but to remain shut up in it as in a prison, under the penalty of losing both his crown and his life. Whilst the Greeks were thus trembling in the presence of the Turks, the janissaries passed through the straits of Thermopylæ without obstruction, and advanced into the Peloponnesus. On the other side, Bajazet, for whom the rapidity of his conquests procured the surname of _Iberim_, or _Lightning_, invaded the country of the Servians, afterwards that of the Bulgarians, and was preparing to carry the war into Hungary.