Meantime the autumnal equinox was approaching, and the weather was becoming cold.  The Medes and Parthians, under their respective monarchs, hung about him, impeded his movements, and cut off his stragglers, but carefully avoided engaging him in a pitched battle.  If he could have forced the city to a surrender, he would have been in comparative safety, for he might have gone into winter quarters there and have renewed the war in the ensuing spring.  But all his assaults, with whatever desperation they were made, failed; and it became necessary to relinquish the siege and retire into Armenia before the rigors of winter should set in.  He could, however, with difficulty bring himself to make a confession of failure, and flattered himself for a while that the Parthians would consent to purchase his retirement by the surrender of the Crassian captives and standards.  Having lost some valuable time in negotiations, at which the Parthians laughed, at length, when the equinox was passed, he broke up from before Praaspa, and commenced the work of retreat.  There were two roads by which he might reach the Araxes at the usual point of passage, One lay towards the left, through a plain and open country, probably that through which he had come; the other, which was shorter, but more difficult, lay to the right, leading across a mountain-tract, but one fairly supplied with water, and in which there were inhabited villages.  Antony was advised that the Parthians had occupied the easier route, expecting that he would follow it, and intended to overwhelm him with their cavalry in the plains.  He therefore took the road to the right through a rugged and inclement country—­probably that between Tahkt-i-Suleiman and Tabriz—­and, guided by a Mardian who knew the region well, proceeded to make his way back to the Araxes.  His decision took the Parthians by surprise, and for two days he was unmolested.  But by the third day they had thrown themselves across his path; and thenceforward, for nineteen consecutive days, they disputed with Antony every inch of his retreat, and inflicted on him the most serious damage.  The sufferings of the Roman army during this time, says a modern historian of Rome, were unparalleled in their military annals.  The intense cold, the blinding snow and driving sleet, the want sometimes of provisions, sometimes of water, the use of poisonous herbs, and the harassing attacks of the enemy’s cavalry and bowmen, which could only be repelled by maintaining the dense array of the phalanx or the tortoise, reduced the retreating army by one-third of its numbers.  At length, after a march of 300 Roman, or 277 British, miles, they reached the river Araxes, probably at the Julfa ferry, and, crossing it, found themselves in Armenia.  But the calamities of the return were not yet ended.  Though it was arranged with Artavasdes that the bulk of the army should winter in Armenia, yet, before the various detachments could reach their quarters in different parts of the country, eight thousand