The sixth century BCE is known as an era of Second Urbanisation in the Indian Subcontinent. After the decline of the Harappan towns and nearly after a gap of more than a thousand years, urban centres emerged again but not in the Indus plain.

• The centre of economic and political activity shifted from the North-West, Punjab, Haryana, and Western UP, to Eastern UP and Bihar (Ganga Basin).
• This region was not only fertile on account of better rainfall and river systems, but was also closer to the iron production centres.
• The new iron agricultural tools and implements (such as the ploughshare) enabled the people to clear thick forest cover and cultivate the hard soil of this area.
• Also, iron weapons made the warrior class more important, and slowly, people gained a strong allegiance to the territory they belonged to rather than the Jana or tribe.
• The use of better iron tools and weapons enabled some territorial states to become very large, and they came to be called Mahajanapadas (large territorial states) in North India (cities and states became visible in South India a few centuries later).
• Most of the Mahajanapadas were situated in the north of Vindhyas, between Bihar in the east to the north-west frontier of the subcontinent.