The Persian and Roman empires were at this time nearly equal in power and civilisation; both were ruled by princes whose reigns form national epochs, yet history affords ample evidence that the brilliant exploits of both these sovereigns were effected by a wasteful expenditure of the national resources and by a consumption of the lives and capital of their subjects which proved irreparable. Neither empire was ever able to regain its former state of prosperity, nor could society recover the shock which it had received. The governments were too demoralised to venture on political reforms, and the people too ignorant and too feeble to attempt a national revolution. The governments of declining countries often give but slight signs of their weaknesses and approaching dissolution as long as the ordinary relations of war and peace require to be maintained only with habitual friends or enemies, though the slightest exertion, created by extraordinary circumstances, may cause the political fabric to fall to pieces. The armies of the Eastern Empire and of Persia had, by long acquaintance with the military force of one another, found the means of balancing any peculiar advantage of their enemy by a modification of tactics, or by an improvement in military discipline, which neutralised its effect. War between the two states was consequently carried on according to a regular routine of service, and was continued during a succession of campaigns in which much blood and treasure were expended, and much glory gained, with very little change in the relative military power, and none in the frontiers, of the two empires. [Sidenote: [527-532 A.D.]] The avarice of Justinian, or his inconstant plans, often induced him to leave the eastern frontier of the empire very inadequately garrisoned; and this frontier presented an extent of country against which a Persian army, concentrated behind the Tigris, could choose its point of attack. The option of carrying the war into Syria, Mesopotamia, Armenia, or Colchis generally lay with the Persians; and Chosroes attempted to penetrate into the empire by every portion of this frontier during his long wars. The Roman army, in spite of the change which had taken place in its arms and organisation, still retained its superiority.[b]