The problem of numbers had been earlier recognised, but
not more adequately met. Diocletian is said to have quadrupled the armies, and
in the fourth century they were far larger than they had been under Julius and
Augustus; Constantine had revised the scheme of frontier-defence to secure the
greatest possible economy of men. Still, under Honorius, we find that one vital
point could only be defended by withdrawing troops from another. The difficulty
of increasing the numbers was twofold. First, the army was mercenary, and
taxation was already strained to the point of diminishing returns. Secondly, it
was difficult to raise recruits among the provincials. The old principle of
universal service had been abandoned by Valentinian I (364-375); and although
compulsory levies were still made from certain classes, the Government had
thought fit to prohibit the enlistment of those who contributed most to taxation.
Every citizen was legally liable for the defence of local strongholds; but the
use of arms was so unfamiliar, the idea of military service as a national duty
was so far forgotten, that Stilicho, when the barbarians were actually in
Italy, preferred the desperate measure of enlisting slaves to the obvious
resource of a general call to arms. We find ourselves here confronted with a
social malady which was more than an economic weakness. The Empire was, no
doubt, a complex and expensive form of government superimposed upon a society
which stood at a rudimentary stage of economic development. Barbarous methods
of taxation and corrupt practices among the ruling classes had aggravated the
burden to such a degree that the municipalities of the provinces were bankrupt,
and the middle-class capitalist was taxed out of existence. For this and other
reasons the population of the older provinces was stationary or declining. But
there was still much wealth in the Empire; and the great landowners of the
provinces could raise considerable armies among their dependants when they saw
fit to do so. The real evil was a moral evil, the decay of civic virtue.