HYDASPES, BATTLE OF THE (326 B.c.). The battle of the Hydaspes (Jhelum) is the most interesting of the four great battles fought by Alexander, since he was not only faced by a well-organized enemy protected by a river in flood but by a force of war elephants against which his decisive arm—heavy cavalry— was useless. Porus, his adversary, occupied the left bank of the river; he was a man of courage and sense, the most efficient gen eral Alexander ever met. According to Diodorus, his army con sisted of 5o,000 infantry, 3,00o cavalry, about i,000 chariots and 13o elephants.
Alexander was encamped near modern Jalapur, the left bank of the river being picketed by the Indians. As he was not able to force a crossing, he divided his army into many parts and laid in a great store of corn in order to make Porus believe that he did not intend to cross until the winter had set in. In any case he could not cross in face of Porus, since the elephants drawn up on the far bank "by their aspect and trumpeting" would have caused his horse to take panic ; he therefore resolved to steal a crossing under the cover of the following stratagem. He sent parties of cavalry up and down the river to make every kind of noise, Forus marching along the opposite bank where the clamour was heard. After a time, nothing taking place, Porus "perceiving that his fear had been groundless" kept his position in his camp. Having thus stupefied his adversary, Alexander determined to make a night march and cross the river at a bend some 18 miles not th of modern Jhelum. He left Craterus in camp with the bulk of the army, instructing him not to attempt to force a passage un less Porus moved away; then, at the head of 5,000 horse and some 9,00o foot, he set out northwards to the point of crossing where skin-raf is and pontoons had been secreted. The river was success fully crossed, and, once the army was marshalled, Alexander ad vanced at the head of the cavalry ordering the infantry to follow on at a slow pace in regular formation. His object undoubtedly was to fix his enemy before he could deploy or retire.
Preliminary Engagement.—Porus, still seeing a large force in Alexander's camp, on hearing that a crossing of the river had been effected by the enemy, sent forward his son at the head of 2,000 cavalry and 120 chariots to delay them. On seeing this force approach, Alexander at first thought that it was Porus himself, and sent out his horse archers to reconnoitre. Learning, however, that it was but a detachment, he charged home killing Porus's son and 400 of his men. Apprised of this defeat, Porus was in doubt what to do. Craterus was now attempting to cross the river, and Alexander was advancing on him at top speed. Leaving some elephants and a small force to watch the ford, he moved off the clayey ground, and deployed his elephants into line at intervals of about 1 oo feet. Behind these he drew up his infantry in pha langial order. On the flanks he posted forces of cavalry, infantry and his chariots.
Seeing the Indians drawn up in order of battle, Alexander halted his cavalry so that his infantry might come up, and then, after resting them, he determined to advance against the enemy's left wing, and so avoid the elephants. His plan was as follows : The horse archers were to move against the enemy's left to throw his cavalry into confusion. Under cover of this fire the Compan ion cavalry were to move against this same wing, and attack the Indian cavalry "while still in a state of disorder." By moving the bulk of his cavalry against the enemy's left wing he foresaw that Porus would probably withdraw his right wing cavalry to support his left wing, and so uncover his right wing. To take advantage of this probability he ordered Coenus and a force of horse, di rectly he saw Porus move his right wing cavalry, to gallop round the enemy's right wing and charge it in rear. The phalanx and the archers were ordered not to engage "until they observed the enemy's cavalry and phalanx of infantry thrown into disorder by the cavalry under his command." The Battle.—To understand the battle as described by Arrian it must be presumed that Porus wheeled back the left of his army to meet the approaching attack, and that he drew his elephants more and more from his right towards his left. With his right wing cavalry he did exactly what Alexander had foreseen, where upon Coenus galloped round the rear of the Indian infantry, and, as Arrian says, "threw the ranks as well as the decisions of the Indians into confusion." To counter this charge Porus wheeled round his cavalry to meet it, whereupon Alexander, seeing his opportunity, charged home at the head of his Companions and drove the enemy back onto their elephants "as to a friendly wall for refuge." The elephants thrown into confusion were neverthe less urged forward by their mahouts, whereupon the phalanx, covered by the archers, charged down on them, but itself became disorganized. The Indian cavalry, seeing this, wheeled round to charge, but Alexander had once again reorganized his cavalry, and charging the Indian cavalry, cut them down in great numbers. One by one the mahouts were killed, and "when the beasts were tired out . . . they began to retire slowly, facing the foe like ships backing water, merely uttering a shrill piping sound." Alex ander now surrounded the whole of the enemy's line with his cavalry, and, giving the signal to the infantry to link shields, he charged his disorganized foe, and won the battle after eight hours fierce contest. The pursuit was at once taken up by Craterus. According to Diodorus the Indian losses were 12,000 and Alex ander's 980.
Tactics.—The first point which strikes the student is the pre paratory moral attack made by Alexander on Porus by a series of feints which blind him by tiring out his vigilance. Directly this has been accomplished, he sets out at the head of a small force; he did not require a large one, because the whole idea of his at tack was based on surprise. For surprise to prove successful, it was essential that Porus should not notice any serious reduction in the numbers opposed to him; consequently, when he learnt of Alexander's advance, he did not realize what was happening. In brief, it was because Craterus was so strong that the surprise of the smaller force was so complete. Alexander's main problem was, seeing that he could not attack the Indian front, which of its two flanks should he select. His army was so small that he must main tain touch with Craterus, and if he could turn Porus's left flank he would facilitate the crossing of the river by Craterus. He de cided to concentrate against the enemy's left flank, and to assist this concentration he detached Coenus, for by this economical distribution of force he added vastly to his main blow which was delivered under cover of demoralization due to surprise. Secured on his right flank by the river and his main army which threatened the Indian rear, he protected the left of his cavalry by the phalanx, and prepared his assault by the fire of his horse archers. Then in oblique order he converged on the enemy's left. As the enemy cavalry was scattered the phalanx approached and with it he de livered a left-hand punch under cover of which he withdrew his cavalry—his right-hand punch. No sooner was this done, than he withdrew his phalanx, and charged home with his cavalry. Then with his phalanx (his left) he knocked his antagonist out.
(J. F. C. F.)