For some centuries it had been more economical to purchase the service of the barbarians than to employ native troops; and perhaps, if the oppressive system of the imperial administration had not impaired the resources of the state and diminished the population by consuming the capital of the people, this might have long continued to be the case. Native troops were always drawn from the mountainous districts, which paid a scanty tribute, and in which the population found difficulty in procuring subsistence. The invasions of the barbarians, likewise, threw numbers of the peasantry of the provinces to the south of the Danube out of employment, and many of these entered the army. A supply of recruits was likewise obtained from the idle and needy population of the towns. The most active and intelligent soldiers were placed in the cavalry--a force that was drilled with the greatest care, subjected to the most exact discipline, and sustained the glory of the Roman arms in the field of battle. As the higher and middle classes in the provinces had, for ages, been excluded from the military profession, and the army had been at last composed chiefly of the rudest and most ignorant peasants, of enfranchised slaves, and naturalised barbarians, military service was viewed with aversion; and the greatest repugnance arose among the civilians to become soldiers. In the meantime, the depopulation of the empire daily increased the difficulty of raising the number of recruits required for a service which embraced an immense extent of territory and entailed a great destruction of human life. The troops of the line, particularly the infantry, had deteriorated considerably in Justinian’s time; but the artillery and engineer departments were not much inferior, in science and efficiency, to what they had been in the best days of the empire. Military resources, not military knowledge, had diminished. The same arsenals continued to exist; mere mechanical skill had been uninterruptedly exercised; and the constant demand which had existed for military mechanicians, armourers, and engineers had never allowed the theoretical instruction of this class to be neglected, nor their practical skill to decline from want of employment. This fact requires to be borne in mind.