Mahajanapadas

The political structure of the ancient Indians appears to have started with semi-nomadic tribal units called Jana (meaning subjects). 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:
Kasi
Kosala
Anga
Magadha
Vajji (or Vriji)
Malla
Chedi
Vatsa (or Vamsa)
Kuru
Panchala
Machcha (or Matsya)
Surasena
Assaka
Avanti
Gandhara
Kamboja
Another Buddhist text Digha Nikaya mentions only first twelve Mahajanapadas and omits the last four in the above list (Digha Nikaya, Vol II, p 200).
Chulla-Niddesa, another ancient text of the Buddhist canon, adds Kalinga to the list and substitutes Yona for Gandhara, thus listing the Kamboja and the Yona as the only Mahajanapadas from Uttarapatha.
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.
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.
The Kasis were Aryan people who had settled in the region around Varanasi (modern Banaras). The capital of Kasi was at Varanasi. The city was bounded by rivers Varuna and Asi on north and south which gave Varanasi its name. Before Buddha, Kasi was the most powerful of the sixteen Mahajanapadas. Several Jatakas bear witness to the superiority of its capital over other cities of India and speaks high of its prosperity and opulence. The Jatakas speak of long rivalry of Kasi with Kosala, Anga and Magadha. A struggle for supremacy went on among them for a time.King Brihadratha of Kasi had conquered Kosala but Kasi was later incorporated into Kosala by King Kansa during Buddha's time. The Kasis along with the Kosalas and Videhans find mention in Vedic texts and appear to have been a closely allied people. Matsya Purana and Alberuni read Kasi as Kausika and Kaushaka respectively. All other ancient texts read Kasi.