Warmatrix

The battle of the Hydaspes (Jhelum) river was fought between Alexander the Great and the Indian king Porus in 326 BCE. It was the first battle where the Macedonians encountered war elephants on a large scale.
In the years before Hydaspes Alexander the Great had conquered the Persian empire, but he did not stop there. Having arrived at its eastern borders, he wanted to include India into his empire. Several tribes in Kashmir, impressed by tales of his conquests, readily surrendered. But a king called Porus was not so easily overpowered. He decided to try to stop the conqueror at the river Jhelum, which the Macedonians called the Hydaspes. Alexander moved quickly, leaving the major part of his army, which at the time had grown very large, behind. The Macedonians had arrived during the start of the monsoon season and the river was already somewhat swollen with water. He was looking for a place where it could be forded, but Porus shadowed his every move on the opposite bank. Eventually a suitable ford was found. Alexander left part of his army at the crossing under command of general Craterus and marched upstream under the cover of night. Craterus lightened many fake campfires to make it seem like the greater part of the army was with him. Halfway the march another part was split off under command of Meleager. Alexander himself crossed the river further upstream with airbags, boats and a pontoon bridge, initially mistaking Admana island for the opposite riverbank.
Eventually Porus heard about the move and sent his son with a small cavalry and chariot force to stop the attackers. But the chariots got stuck in the river mud and the cavalry were beaten back; Porus' son was killed. Porus realized that the main part of his enemy had crossed the river and marched to meet them, in his turn leaving a small detachment to guard against any movement from Craterus.
In daylight, the two main forces met in battle. The Indian army is estimated at 30,000 infantry, 4,000 cavalry, 300 chariots and 200 elephants. Porus put his chariots and cavalry on the flanks and elephants in the center, before the infantry. Alexander did not attack right away, but secured the middle river crossing and waited for Meleager's force to join up. After that, the Macedonians numbered 22,000 infantry and 6,000 cavalry. Alexander deployed these forces in a less broad, more dense formation with most cavalry on the right.
His army by this time had plenty of Persian horse archers and he opened the battle by sending them to harass the Indian left wing. This drew in the Indian cavalry and Alexander followed up with a heavy cavalry charge. Porus sent his own right flank cavalry to help his hard-pressed troops out, but to no avail. Many Indian cavalrymen sough refuge amidst their infantry line, disorganizing it. Freed of opponents, the Macedonian cavalry on the left under command of Coenus rode around the main battle line and attacked the Indians in the rear. Another unit of cavalry had circled round on the other flank and did likewise. Porus saw that his cavalry was losing and ordered his elephants and infantry to move forward. Archers and peltasts attacked the eyes and feet of the elephants and also their drivers. Many got out of control and attacked everybody around them, but most kept going forward and caused losses among the Macedonian phalanx. But the cavalry attacks from the rear, joined by Alexander's Companions from the left, hemmed in the Indians on all sides. The elephants stampeded in all directions. Soon after the Indian army disintegrated completely and was beaten. Craterus crossed the river too and helped chase down fleeing enemies.
Indian losses were more than 20,000 infantry and 3,000 cavalry, including two sons of Porus and many of his generals. Alexander was so impressed by Porus' fighting spirit that he made him governor of the now conquered Punjab, so that he could rule his old kingdom again, though now under a master. Despite their victory, Macedonian losses were significant too, probably around 1,000. This, combined with losses on the campaign, the unforgiving monsoon weather and the fierce resistance of the Indians before and during the battle, brought the morale of the army down. When Alexander expressed his desire to attack the Nanda empire next, it mutinied and forced him to turn back to the west.
The battle is remarkable because the elephants initially prevented the Macedonian phalanx from engaging, making the first half almost a pure cavalry fight. Only when the Macedonians had gained the upper hand and managed to disorganize the main Indian line, could the infantry move in. The battle shows both the strengths and the weaknesses of war elephants. The Macedonians were impressed by them and Alexander's successors used them in many battles.