The great national standard was the famous “leathern apron of the blacksmith,” originally unadorned, but ultimately covered with jewels, which has been described in a former chapter.  This precious palladium was, however, but rarely used, its place being supplied for the most part by standards of a more ordinary character.  These appear by the monuments to have been of two kinds.  Both consisted primarily of a pole and a cross-bar; but in the one kind the crossbar sustained a single ring with a bar athwart it, while below depended two woolly tassels; in the other, three striated balls rose from the cross-bar, while below the place of the tassels was taken by two similar balls.  It is difficult to say what these emblems symbolized, or why they were varied.  In both the representations where they appear the standards accompany cavalry, so that they cannot reasonably be assigned to different arms of the service.  That the number of standards carried into battle was considerable may be gathered from the fact that on one occasion, when the defeat sustained was not very complete, a Persian army left in the enemy’s hands as many as twenty-eight of them.

During the Sassanian period there was nothing very remarkable in the Persian tactics.  The size of armies generally varied from 30,000 to 60,000 men, though sometimes 100,000, and on one occasion as many as 140,000, are said to have been assembled.  The bulk of the troops were footmen, the proportion of the horse probably never equalling one third of a mixed army.  Plundering expeditions were sometimes undertaken by bodies of horse alone; but serious invasions were seldom or never attempted unless by a force complete in all arms; comprising, that is, horse, foot, elephants, and artillery.  To attack the Romans to any purpose, it was always necessary to engage in the siege of towns; and although, in the earlier period of the Sassanian monarchy, a certain weakness and inefficiency in respect of sieges manifested itself, yet ultimately the difficulty was overcome, and the Persian expeditionary armies, well provided with siege trains, compelled the Roman fortresses to surrender within a reasonable time.  It is remarkable that in the later period so many fortresses were taken with apparently so little difficulty—­Daras, Mardin, Amida, Carrhse, Edessa, Hierapolis, Berhasa, Theodosiopolis, Antioch, Damascus, Jerusalem, Alexandria, Caesaraea Mazaca, Chalcedon; the siege of none lasting more than a few months, or costing the assailants very dear.  The method used in sieges was to open trenches at a certain distance from the walls, and to advance along them under cover of hurdles to the ditch, and fill it up with earth and fascines.  Escalade might then be attempted; or movable towers, armed with rams or balistae, might be brought up close to the walls, and the defences battered till a breach was effected.  Sometimes mounds were raised against the walls to a certain height, so that their upper portion, which was their weakest part, might be attacked, and either demolished or escaladed.  If towns resisted prolonged attacks of this kind, the siege was turned into a blockade, lines of circumvallation being drawn round the place, water cut off, and provisions prevented from entering.  Unless a strong relieving army appeared in the field, and drove off the assailants, this plan was tolerably sure to be successful.