In the autumn of 325, Alexander led his men through the Gedrosian desert. Many people died, although we must assume that not the soldiers, but the women, merchants and animals in the train were the main victims. The following description is taken from the Anabasis of the Greek author Arrian of Nicomedia; section 6.24.1-26.5 was translated by Aubrey de Sélincourt.
Alexander in the Gedrosian desert
[6.24.1] The next objective was the capital town of Gedrosia, situated in a district named Pura. The march thither from Oria occupied in all sixty days. Most historians of Alexander's campaigns have stated that the sufferings of his men on that march were out of all proportion greater than anything they had had to endure in Asia.
[6.24.2] Alexander did not choose that route because he was unaware of the difficulties it would involve (Nearchus is our one authority for this); he chose it because, apart from [the legendary queen] Semiramis on her retreat from India, no man, to his knowledge, had ever before succeeded in bringing an army safely through. Even Semiramis, according to local tradition, got through with no more than twenty survivors, and Cyrus, son of Cambyses, with only seven
[6.24.3] - for it is a fact that Cyrus came here with the intention of invading India, but found the going so bad and the country so wild and barren that he lost nearly all his men before he could do so. Alexander heard these old stories; they inspired him to go one better than Cyrus and Semiramis, and that was the reason, combined with the hope of being able to keep contact with the fleet and procure supplies for it, why, according to Nearchus, he marched by that route.
[6.24.4] The result was disastrous: the blazing heat and the lack of water caused innumerable casualties, especially among the animals, most of which died of thirst or from the effects of the deep, burning, sun-baked sand. Sometimes they met with lofty hills of sand - loose, deep sand, into which they sank as if it were mud or untrodden snow; sometimes, climbing or descending, the mules and horses suffered even greater distress from the uneven and treacherous surface of the track.
[6.24.5] Not the least hardship was the varying length of the marches, as the fact that they never knew when they would find water made regular, normal marches impossible.
[6.24.6] It was not so bad when they found water in the morning after covering the requisite distance during the night; but when there was still further to go, and they found themselves plodding on and on as the day advanced, the double distress of heat and raging thirst was almost intolerable.
[6.25.1] Casualties among the animals were very numerous; indeed, most of them perished. Often they were killed deliberately by the men, who used to put their heads together and agree to butcher the mules and horses, whenever supplies gave out, and then eat their flesh and pretend they had died of thirst or exhaustion. As every man was involved, and the general distress was so great, there was no one to bring actual evidence of this crime,
[6.25.2] though Alexander himself was not unaware of what was going on; he realized, however, that the only way to deal with the situation was to feign ignorance, which would be better than to let the men feel that he connived at their breach of discipline.
It was, moreover, no easy task, when men were sick or fell exhausted in their tracks, to get them along with the rest; for there were no transport animals left and even the wagons were being continually broken up as it became more and more impossible to drag them through the deep sand. In the earlier stages of the march they had often been prevented for this reason from taking the shortest route and compelled to seek a longer one which was more practicable for the teams.
[6.25.3] So there was nothing for it but to leave the sick by the way, and any man rendered incapable by exhaustion or thirst or sunstroke. No one could give them a helping hand; no one could stay behind to ease their sufferings, for the essential thing was to get on with all possible speed, and the effort to save the army as a whole inevitably took precedence over the suffering of individual men.
Most of the marching was at night, and many men would fall asleep in their tracks; the few who had strength left to do so followed the army when they woke up again, and got safe through; but the greater number perished - poor castaways in the ocean of sand.
[6.25.4] There was yet another disaster, perhaps the worst for all concerned, men, horses, and mules. In Gedrosia, as in India, it rains heavily during the monsoon; the rain falls not on the plains but on the mountains, the summits of which arrest the clouds carried thither by the wind and cause them to condense in rain.
[6.25.5] It so happened that the army bivouacked by a small stream, for the sake of the water it afforded, and about the second watch of the night it was suddenly swollen by rain. The actual rain was falling far away out of sight, but the stream nevertheless grew into such a torrent that it drowned most of the camp-followers' women and children and swept away the royal tent with everything it contained, and all the surviving animals, while the troops themselves barely managed to escape, saving nothing but their weapons - and not even all of those.
[6.25.6] Another trouble was, that when plenty of water happened to be found after a hot and thirsty march, most of the men drank so immoderately that the result was fatal to them, and for this reason Alexander usually made his halts a couple of miles or so from water, to stop his men from flinging themselves indiscriminately upon it to their own destruction and that of their hearts, and to prevent those who had least self-control from plunging right into the spring or stream, or whatever it was, and so spoiling the water for the others.
[Arrian continues with the well-known story of Alexander refusing fresh water. This incident probably took place in the Bactrian desert: more...]
[6.26.4] To add to their difficulties, the time came when the guides admitted that they no longer knew the way; all the marks, they declared, had been obliterated by the blown and drifting sand. There was nothing in the vast and featureless desert to determine what course they should take - no trees, as elsewhere, by the roadside, no hills of solid earth rising from the sand. Moreover, the guides had never practiced the art of finding their direction by the stars at night and by the sun in the day-time, as sailors do - the Phoenicians setting their course by the Little Bear, the rest of us by the Great Bear.
[6.26.5] Alexander, accordingly, took the matter into his own hands; feeling that the route should be more towards the left, he rode ahead with a small party of mounted men. The horses soon began to succumb to the heat, so he left most of his party behind and rode off with only five men. At last they found the sea, and scraping away the shingle on the beach came upon fresh, clear water. The whole army soon followed, and for seven days marched along the coast, getting its water from the beach. Finally the guides once more recognized their whereabouts, and a course wag set for the interior again.