Ancient Greek Polis
From India, military thinking on the use of war elephants spread westwards to the Persian Empire, where they were used in several campaigns and in turn came to influence the campaigns of Alexander the Great. The first confrontation between Europeans and the Persian war elephants occurred at Alexa nder's Battle of Gaugamela (331 BC), where the Persians deployed fifteen elephants. These elephants were placed at the centre of the Persian line and made such an impression on Alexander's army that he felt the need to sacrifice to the God of Fear the night before the battle – but according to some sources the elephants ultimately failed to deploy in the final battle owing to their long march the day before. Alexander won resoundingly at Gaugamela, but was deeply impressed by the enemy elephants and took these first fifteen into his own army, adding to their number during his capture of the rest of Persia.
By the time Alexander reached the borders of India five years later, he had a substantial number of elephants under his own command. When it came to defeating Porus, who ruled in what is now Punjab, Pakistan, Alexander found himself facing a considerable force of between 85 and 100 war elephants at the Battle of the Hydaspes. Preferring stealth and mobility to sheer force, Alexander manoeuvered and engaged with just his infantry and cavalry, ultimately defeating Porus' forces, including his elephant corps, albeit at some cost. Porus for his part placed his elephants individually, at long intervals from each other, a short distance in front of his main infantry line, in order to scare off Macedonian cavalry attacks and aid his own infantry in their struggle against the phalanx. The elephants caused many losses with their tusks fitted with iron spikes or by lifting the enemies with their trunks and trampling them.
Arrian described the subsequent fight: "Whenever the beasts could wheel around, they rushed forth against the ranks of infantry and demolished the phalanx of the Macedonians, dense as it was."
The Macedonians adopted the standard ancient tactic for fighting elephants, loosening their ranks to allow the elephants to pass through and assailing them with javelins as they tried to wheel around; they managed to pierce the unarmoured elephants' legs. The panicked and wounded elephants turned on the Indians themselves; the mahouts were armed with poisoned rods to kill the beasts but were slain by javelins and archers.
Looking further east again, however, Alexander could see that the kings of the Nanda Empire and Gangaridai could deploy between 3,000 and 6,000 war elephants. Such a force was many times larger than the number of elephants employed by the Persians and Greeks, which probably discouraged Alexander's army and effectively halted their advance into India. On his return, Alexander established a force of elephants to guard his palace at Babylon, and created the post of elephantarch to lead his elephant units.
The successful military use of elephants spread further. The successors to Alexander's empire, the Diadochi, used hundreds of Indian elephants in their wars, with the Seleucid Empire being particularly notable for their use of the animals, still being largely brought from India.