To secure the frontiers, Justinian adopted a plan of constructing extensive lines supported by innumerable forts and castles, in which he placed garrisons, in order that they might be ready to sally out on the invading bands. These lines extended from the Adriatic to the Black Sea, and were further strengthened by the long wall of Anastasius, which covered Constantinople by walls protecting the Thracian Chersonesus and the peninsula of Pallene, and by fortifications at Thermopylæ, and at the Isthmus of Corinth, which were all carefully repaired. At all these posts permanent garrisons were maintained. The eulogy of Procopius on the public edifices of Justinian seems almost irreconcilable with the events of the latter years of his reign; for Zabergan, king of the Huns, penetrated through breaches he found unrepaired in the long wall, and advanced almost to the very suburbs of Constantinople. Another instance of the declining state of military tactics may be mentioned, as it must have originated in the army itself, and not in consequence of any arrangements of the government. The combined manœuvres of the divisions of the regiments had been so neglected that the bugle-calls once used had fallen into desuetude, and were unknown to the soldiers. The motley recruits, of dissimilar habits, could not acquire with the requisite rapidity a perception of the delicacy of the ancient music, and the Roman infantry no longer moved “In perfect phalanx, to the Dorian mood, Of flutes and soft recorders.” It happened, during the siege of Auximum in Italy, that Belisarius was placed in difficulty from the want of an instantaneous means of communicating orders to the troops engaged in skirmishing with the Goths. On this occasion it was suggested to him by Procopius, his secretary and the historian of his wars, to replace the forgotten bugle-calls by making use of the brazen trumpet of the cavalry to sound a charge, and of the infantry bugle to summon a retreat.