During the life time of Lord Gautam Buddha, sixteen great powers (Mahajanpadas/Mahajanapadas) existed in the 7th and early 6th centuries BC. Among the more important republics were the Sakyas of Kapilavastu and the Licchavis of Vaishali. Besides the republics, there were monarchical states, among which the important ones were Kaushambi (Vatsa), Magadha, Kosala and Avanti. These states were ruled by vigorous personalities who had embarked upon the policies of aggrandisement and absorption of neighbouring states. However, there were distinct signs of the republican states while those under the monarchs were expanding.
The political structure of the ancient Indo-Aryans appears to have started with semi-nomadic tribal units called "Jana". Early Vedic texts attest several Janas or tribes of the Aryans, living in semi-nomadic tribal state, fighting among themselves and with other Non-Aryan tribes for cows, sheep and green pastures. These early Vedic Janas later coalesced into Janapadas of the Epic Age.
The term "Janapada" literally means the foothold of a tribe. The fact that Janapada is derived from Jana points to an early stage of land-taking by the Jana tribe for a settled way of life. This process of first settlement on land had completed its final stage prior to the times of Buddha and Panini. The Pre-Buddhist North-west region of Indian sub-continent was divided into several Janapadas demarcated from each other by boundaries. In Panini, Janapada stands for country and Janapadin for its citizenry. These Janapadas were named after the tribes or the Janas who had settled in them. By circa 600 BCE, many of these Janapadas had further evolved into larger political entities by the process of land-grabbing which eventually led to the formation of kingdoms known in Buddhist traditions as the Mahajanapadas or the great nations (Sanskrit: Maha = great, Janapada = country).
The Buddhist and other texts only incidentally refer to sixteen great nations (Solasa Mahajanapadas) which were in existence before the time of Buddha. They do not give any connected history except in the case of Magadha. The Buddhist Anguttara Nikaya, at several places, gives a list of sixteen nations:
5. Vajji (or Vriji)
8. Vatsa (or Vamsa)
11. Machcha (or Matsya)
The Jaina Bhagvati Sutra gives slightly different list of sixteen Mahajanapadas viz: Anga, Banga (Vanga), Magadha, Malaya, Malavaka, Accha, Vaccha, Kochcha (Kachcha), Padha, Ladha (Lata), Bajji (Vajji), Moli (Malla), Kasi, Kosala, Avaha and Sambhuttara. Obviously, the author of Bhagvati has a focus on the countries of Madhydesa and of far east and south only. He omits the nations from Uttarapatha like the Kamboja and Gandhara. The more extended horizon of the Bhagvati and the omission of all countries from Uttarapatha clearly shows that the Bhagvati list is of later origin and therefore less reliable (Political History of Ancient India, 1996, p 86; History & Culture of Indian People, Age of Imperial Unity, p 15-16).
The main idea in the minds of those who drew up the Janapada lists was basically more tribal than geographical, since the lists include names of the people and not the countries. As the Buddhist and Jaina texts only casually refer to the Mahajanapadas with no details on history, the following few isolated facts, at best, are gleaned from them and other ancient texts about these ancient nations.