Alexander’s campaign to conquer the Persian Empire had begun in the spring of 334 BCE and was successfully concluded 328 BCE with the defeat of Bessos, the Satrap of Bactria, and the Sogdian warlord Spitamenes. Alexander then launched a campaign into the Indian subcontinent in 327 BCE. His army was some 45,000 strong, including 40,000 infantry and 5,000 cavalry. As they approached the Hydaspes River in modern-day Pakistan they saw the Indian king, Porus, deploying on the far bank ready to oppose any attempt to cross. While Alexander tset about finding a suitable crossing point, his commander Craterus and his troops were left behind to make highly visible moves along the north bank, engaging the attention of King Porus who shadowed the Macedonian movements. Meanwhile Alexander, with about 6,000 infantry and 5,000 cavalry, found a suitable crossing place some 27 km (c.17 miles) upstream. Alexanders’ force, utterly defeated a smaller Indian scouting force, commanded by Porus, the son of King Porus, who was killed. Alexander now deployed his cavalry aimed at the Indian army’s flanks, while the Macedonian infantry began their advance. The advancing Macedonian infantry now came into close combat with armoured war elephants, an unfamiliar enemy which initially caused terrible casualties. With grim determination, the long spears of the Macedonians found gaps in the elephants’ armour, and the creatures stampeded among their own infantry, who fled the battlefield. Craterus, with the rest of the Macedonian army, crossed the river and joined Alexander in defeating the army of King Porus, who fought on until he was wounded and captured.