Its called the beginning of Second Urbanization in India after Harappa Civilization. Though Iron was discovered in Later Vedic phase(1000-600 B. C.) but was used scarcely only to make weapons to fight wars. It was in this Mahajanapada Phase that Iron was used tin agriculture and to clear forests to increase area under agriculture. Due to incresed agricultural surplus, the system of Taxation started, now standing armies can be maintained from the agricultural surplus, cities came up. These cities became the urban centres in India where people who were not dependent agriculture lived and thus trade activities started and thus small kingdoms developed in these cities. These were 16 in number and earlier Kashi and Kosala were the strongest (Avanti was in the Deccan region and was also strongest) and wealthiest but later Magadhareplaced them to establish a pan-India empire under Mauryas. Their strength lied in their close proximity to a large number of forest resources and also to Iron producing areas in present day Jharkhand. Though Avanti for a long time posed a challenge to Magadha empire as it was also in close proximity to Iron ore mines in present day Madhya Pradesh. But due to the interprising nature of the Magadha rulers, they trumped all.

In South India the society was still in Megalithic phase though they knew how to make iron but did little agriculture and were mainly depended on hunting and gathering. It was when the Mauryan empire expanded into South that they came in contact with urbanization and technology ( agricultural, iron and steel etc.) and thus started the Sangama Age of 3 kingdoms in South India namely - the Cheras, the Cholas and the Pandyas in the first 3 Christian centuries.