Priests and nobles appear to have gradually drifted into the belief that resistance was hopeless. Their acquiescence in what they believed to be the inevitable suggests the mediocrity of their leaders. Their merits and faults were alike negative. They were not given over to vice and profligacy; they were not cruel tyrants; they were not wanting in courage; but they were without ability or energy, incapable of initiating or executing any successful plan of campaign against the enemy or of making arrangements for securing efficient foreign aid. It is, of course, easy to suggest after the event that the empire might have been saved, but it is difficult to believe that among the governing class there was not a lack of vitality which contributed to its fall. Looking across the centuries, we may, perhaps, conclude that the empire followed the natural course of evolution under despotic rule: struggle for existence, success, wealth, contentment to the point of stagnation, a general slackness and loss of energy and a reluctance to struggle of any kind. But whether such conclusion be justified or not, it cannot be doubted that weariness of strife and general enervation characterised all classes of society. In remembering this, it may be said that the morale of the empire was destroyed and its population demoralised.[167] [Sidenote: Causes of decay of empire.] Three causes mainly contributed to the diminution and ultimate downfall of the empire: first, the establishment of the Latin empire, with which must be associated (_a_) the internal dissensions among the Greeks themselves, and (_b_) the increased difficulty in assimilating the races occupying the Balkan peninsula; second, the attacks, literally from every side, by hordes of Turkish invaders, who usually, beginning by raids upon their cattle, ended by expelling or exterminating the conquered people and taking possession of their lands; and, third, the depopulation of the Balkan peninsula and of the cities in Asia Minor held by the empire caused by Black Death or Plague. [Sidenote: Latin conquest.]