In 324 b.c.e. Chandragupta Maurya unifi ed northern India by defeating his rivals. He went on to war against the successor of Alexander the Great in Asia, Seleucus Nicator, expelling his forces from the borderlands of India.

In 305 b.c.e. the two men concluded a treaty in which the Greeks withdrew from the Punjab in north-western India and which fixed the western boundary of the Mauryan Empire to the crest of the Hindu Kush. There was also exchange of ambassadors, gifts, and a vague mention of a marriage alliance.

Megasthenes was Seleucus’s representative at Chandragupta’s court. He wrote a detailed account of his observations while in India. Although the original was lost, parts have survived through extensive excerpting in the works of other ancient writers.

Megasthenes described Pataliputra, the Mauryan capital, as second in splendor only to Persepolis, capital of the former Persian Empire. It had a wooden city wall 9 miles long by 1.5 miles wide, which had 570 towers, 64 gates, and a 900-foot-wide moat. He wrote admiringly of Chandragupta as an energetic ruler who personally supervised affairs of state.

The emperor lived in splendor in an enormous palace built of wood, but he also lived in fear of assassination, appearing only rarely in public, attired in a splendid purple and golden robe, and was either carried in a palanquin or rode on an elephant.

He also described the administration of the capital city by six boards each with five men, in charge of crafts and industry, trade and commerce, tax collection, foreigners, collection of statistical information, and public works.

Other information states that a quarter of the people’s produce was paid as taxes and that there were dues assessed on commerce. He described the Mauryan military as having infantry, cavalry, chariots, elephants, navy, and a commissariat. He also commented on the division of people into seven castes by occupation.

One passage on the people’s lives said: "They live happily enough, being simple in their manners, and frugal. They never drink wine except at sacrifice ... The simplicity of their laws and their contracts is proved by the fact that they seldom go to law ... Truth and virtue they hold alike in esteem ... The greater part of the soil is under irrigation, and consequently bear two crops in the course of the year".

Some information Megasthenes provided was wrong, for instance his assertion that there was no slavery in India and that no famines occurred. Nevertheless, his writings on India are valuable because there are few Indian sources on actual life in the period, and his were the first extensive observations by a foreigner.