Callisthenes, held shortly afterward to be privy to a conspiracy against Alexander among the royal pages, is thrown into prison, where he dies in 327; resentment of this action alienates sympathy from Alexander within the Peripatetic school of philosophers, with which Callisthenes, as the nephew of Aristotle, has close connections.

His death is commemorated by his friend Theophrastus in Callisthenes, or a Treatise on Grief.

Alexander leaves Bactria in early summer with a reinforced army under a reorganized command.

If Plutarch's figure of one hundred and twenty thousand men has any reality, however, it must include all kinds of auxiliary services, together with muleteers, camel drivers, medical corps, peddlers, entertainers, women, and children; the fighting strength perhaps stands at about thirty-five thousand.

Recrossing the Hindu Kush, probably by Bamian and the Ghorband Valley, Alexander divides his forces.

Half the army with the baggage under Hephaestion and Perdiccas, both cavalry commanders, is sent through the Khyber Pass, while …

An illegitimate son is born to Alexander by his mistress Barsine, daughter of the satrap Artabazos II of Phrygia.

The first son of Alexander, he is named after the Greek hero Heracles, from whom the Macedonian royal family claims its descent.

At the time of his birth, there is no reason to consider Heracles a possible candidate for the throne.

His father is still twenty-nine years old and about to marry the princess Roxana of Bactria, and there is little doubt at this time that they will produce legitimate heirs to the throne.

Alexander, crossing the Indus near Attock in spring 326, …

…enters prosperous Taxila, whose ruler, Taksilla, furnishes elephants and troops in return for aid against his rival Porus, who rules the lands between the Hydaspes (modern Jhelum) and the Acesines (modern Chenab) rivers.

Porus, unlike his neighbor, Ambhi, the king of Taxila (Taksasila), resists Alexander.

In June, 326, Alexander, faced with a crossing of the Hydaspes (now called Jhetum) River in full flood and hostile Indians, supported by two hundred horse-crazing elephants, on the far side, begins to launch boats and rafts, gather up supplies, and run cavalry exercises.

When he senses the Indians growing lax, he takes across a force of eleven thousand men, leaving the main body encamped.

Employing brilliant tactics, he first employs his mobile cavalry and mounted archers to defeat the Indian chariots, then destroys the bunched, slow-moving infantry, setting his own infantry against the elephants with axes.

Seleucus, the son of Antiochus, a general of Philip, has participated in the conquest of the Persian empire as one of Alexander's officers, and commands the Macedonian infantry in the battle.

Alexander founds two cities on the left bank of the Hydaspes, Alexandria Nicaea (to celebrate his victory) and Bucephala (named after his horse Bucephalus, which dies there).

Impressed by Porus' techniques and spirit, Alexander allows him to retain his kingdom and perhaps even cedes some conquered areas to him.

(Not known in Indian sources, the name Porus has been conjecturally interpreted as standing for Paurava; i.e., the ruler of the Purus, a tribe known in that region from ancient Hindu Vedic times.)

How much Alexander knows of India beyond the Hyphasis (probably the modern Beas) is uncertain; there is no conclusive proof that he has heard of the Ganges River.

Alexander now faces the powerful empire of Magadha ruled by the Nanda dynasty, but he is anxious to press on farther However, his army, fearing the prospects of facing another powerful Indian army and exhausted by years of campaigning, mutinies at the Hyphasis River (the modern Beas River).

Refusing to go farther in the tropical rain, the army is weary in body and spirit, and Coenus, one of Alexander's four chief marshals, acts as their spokesman.

On finding the army adamant, Alexander agrees to turn back, making this river mark the easternmost extent of his conquests.

A short time afterwards, when the Macedonian army had actually commenced its return, Coenus dies of an illness, and is honored by the king with a splendid burial.

Alexander laments his death, but is reported to have said that Coenus had urged the necessity of returning so strongly, it was as if he alone had been destined to see his native country again.

On the Hyphasis, Alexander erects twelve altars to the twelve Olympian gods.

Lycurgus has controlled the Athenian state finances during the dozen years following the Athenian defeat in 338 by Macedonia at Chaeronea, and is said to have doubled the annual public revenues.

He has reformed the constitution of the army, remodeled the fleet, repaired dockyards, and finished the arsenal designed by the architect Philo.

He has carried out an extensive building program (the first since the fifth century), including the reconstruction in stone of the Dionysiac theater.

He also had official copies made of the plays of the three great tragic dramatists, Aeschylus, Sophocles, and Euripides.

The Samnites had supported a faction in a contest for control of Neopolis, now a center of Greek culture in southern Italy.

Rome, currently besieging the city, finally persuades the Samnite garrison to leave, and Neopolis falls to the Romans in 326 BCE.

The city allies with Rome and continues to prosper, but the Samnites renew their war with Rome.

To help defeat the Samnites, the Romans make alliances with the peoples of Central Italy to the north of Samnium and with the Apulians to the southeast.

The Romans soon confronted the Samnites in the middle of the Liris river valley (modern Liri), sparking the Second, or Great, Samnite War, which is to last twenty years and will not be not a defensive venture for Rome.

During the first half of the war Rome would suffer serious defeats, but the second half will see Rome's recovery, reorganization, and ultimate victory.

King Wuling of Zhao, probably the son of Zhao Suhou, ascends to the throne at 325 BCE, about halfway into the Warring Kingdoms Era (Chinese historians refer to this as the period between 481 BCE and 221 BCE).

During the early years of his reign the Kingdom of Zhao is constantly harassed by the Eastern Hu, the Linhu, the Liufan, and the Xiongnu, all wandering tribes.

Up to this time Zhao commanders riding on horseback still wore robes and normal court attire, whereas the Hu uniform of pants, belt, boots, fur caps, and fur clothes is much better adopted to fighting on horseback.

Wuling’s reign is to be famous for a single important event: the reforms consisting of "Wearing Barbarian Uniform and the Use of Cavalry in Battle".