On the third day after the battle, Alexander reached the river Ister, which is the largest of all the rivers in Europe, traverses a very great tract of country, and separates very warlike nations. Most of these belong to the Celtic race,[34] in whose territory the sources of the river take their rise. Of these nations the remotest are the Quadi[35] and Marcomanni[36]; then the Iazygians,[37] a branch of the Sauromatians[38]; then the Getae,[39] who hold the doctrine of immortality; then the main body of the Sauromatians; and, lastly, the Scythians,[40] whose land stretches as far as the outlets of the river, where through five mouths it discharges its water into the Euxine Sea.[41] Here Alexander found some ships of war which had come to him from Byzantium, through the Euxine Sea and up the river. Filling these with archers and heavy-armed troops, he sailed to the island to which the Triballians and Thracians had fled for refuge. He tried to force a landing; but the barbarians came to meet him at the brink of the river, where the ships were making the assault. But these were only few in number, and the army in them small. The shores of the island, also, were in most places too steep and precipitous for landing, and the current of the river alongside it, being, as it were, shut up into a narrow channel by the nearness of the banks, was rapid and exceedingly difficult to stem. Alexander therefore led back his ships, and determined to cross the Ister and march against the Getae, who dwelt on the other side of that river; for he observed that many of them had collected on the bank of the river for the purpose of barring his way, if he should cross. There were of them about 4,000 cavalry and more than 10,000 infantry. At the same time a strong desire seized him to advance beyond the Ister. He therefore went on board the fleet himself. He also filled with hay the hides which served them as tent-coverings, and collected from the country around all the boats made from single trunks of trees. Of these there was a great abundance, because the people who dwell near the Ister use them for fishing in the river, sometimes also for journeying to each other for traffic up the river; and most of them carry on piracy with them. Having collected as many of these as he could, upon them he conveyed across as many of his soldiers as was possible in such a fashion. Those who crossed with Alexander amounted in number to 1,500 cavalry and 4,000 infantry. CHAPTER IV. ALEXANDER DESTROYS THE CITY OF THE GETAE.—THE AMBASSADORS OF THE CELTS.