The Battle of the Hydaspes River was a battle fought by Alexander the Great in 326 BC against the Indian king Porus (Pururava or Purushotthama in Sanskrit) at Kshatriya on the Hydaspes River (the Jhelum) in the Punjab region of ancient India, near Bhera now in Pakistan. The kingdom of Paurava of King Porus was situated in the part of Punjab which is now part of modern day Pakistan (see Pakistani Punjab). The Hydaspes was the last major battle fought by Alexander. Although victorious, Alexander's exhausted army mutinied and refused to go any further into India. His tired army saw the use of war elephants for the first time in years since Gaugamela. King Porus and his men put up a fierce resistance against the invading Macedonian army which even won the admiration and respect of Alexander.
The main train went into modern day Pakistan through the Khyber Pass, but a smaller force under the personal command of Alexander went through the northern route, taking a fortress at Aornos (modern day Pir-Sar, Pakistan) on the way. In early spring of the next year, he combined his forces and allied with Taxiles (also Ambhi), the King of Taxila, against his neighbor, the King of Hydaspes.
Porus drew up on the south bank of the Jhelum River, and was set to repel any crossings. The Jhelum River was deep and fast enough that any opposed crossing would probably doom the entire attacking force. Alexander knew that a direct crossing would fail, and so he tried to find a crossing point. Alexander moved his mounted troops up and down the river bank each night, with Porus shadowing him. Eventually, Alexander found a suitable crossing, about 17 miles upstream of his camp. His plan was a classic pincer maneuver: leave his general Craterus behind with most of the army while Alexander crossed the river upstream with a strong part of his army, consisting perhaps of 10,000 foot and 5,000 horse. Craterus was to ford the river and attack if Porus faced Alexander with all his troops, but to remain if Porus faced Alexander with only a part of his army.
Alexander quietly moved his part of the army upstream and then traversed. He landed on an island, however, but was soon on the other side of the river. To combat the new threat, Porus sent a small cavalry and chariot force under his son to the crossing. The force was easily routed, the chariots in particular being impeded by the mud near the shore of the river, with Porus' son among the dead. Porus now saw that the crossing force was larger, and decided to face it with the bulk of his army. He left behind a small detachment to disrupt the landing of Craterus' force now crossing the river.
These war elephants presented an especially difficult situation for Alexander. Most of his success on the battlefield came from his ability to separate the enemy lines and drive his crack Companion cavalry into the opening. This was used with devastating effectiveness at both Issus and Gaugamela. However, the Indian elephants scared the Macedonian horses. The mere scent of these incredible creatures forced Alexander to modify his strategy.
Alexander started the battle by sending horse archers to shower the Indian left cavalry wing. After this, he led the customary charge on the weakened cavalry wing. Predictably, the Indian right cavalry wing galloped to the opposite wing in order to reinforce the charged cavalry. At this moment, Alexander sent his officer Coenus with cavalry either to attack the Indian left by way of circling behind the enemy, or to attack the Indian cavalry after a feint to the Indian right. Thus, Alexander was able to destroy the Indian cavalry while minimizing his mounted units' exposure to the Indian war elephants. Had the Indian cavalry not been destroyed they could have endangered his phalanxes later in the battle, and the Macedonian horse may not have been able to support the foot soldiers against the Indian cavalry due to the proximity of the elephants.
Meanwhile, the Macedonian phalanxes had advanced to engage the charge of the war elephants, which was stopped, albeit with heavy casualties to the infantry. The Macedonians eventually surrounded the Indian force, which amounted to a mass surrender.
Porus was one of many Indians who impressed Alexander. Wounded in his shoulder, standing at seven feet tall, but still on his feet, he was asked by Alexander how he wished to be treated. "Treat me, O Alexander, like a king" Porus responded.
Macedonian losses to their cavalry arm was much less than in the infantry, with 280 killed. Alexander lost as many as 4,000 infantry, mostly phalanx troops, while 12,000 of his men were casualties in total. They had borne the brunt of the fighting against the elephants, as the horses of the Macedonian cavalry had refused to go near the beasts. Indian losses amounted to 12,000 dead and 9,000 men captured.
The bravery and war skills of Porus impressed Alexander. Alexander spared the life of Porus, although he had been defeated, and let him rule Hydaspes in Alexander's name. This was as far as Alexander could go. At this time, the Magadha Empire further east on the Gangetic plain had 6,000 war elephants. These numbers of war elephants were many times larger than the numbers employed by the Persians and Greeks, which was discouraging for Alexander's men and stayed further progress into India.
Afterwards, Alexander founded Alexandria Nikaia (Victory), located at the battle site, to commemorate his triumph. He also founded Alexandria Bucephalus on the opposite bank of the river. Alexander did this in memory of his recently deceased and much cherished horse, Bucephalus.