The 6th–5th centuries BCE is often regarded as a major turning point in early Indian history,during this period India’s first large cities arose after the demise of the Indus Valley Civilization. It was also the time of the rise of sramana movements (including Buddhism and Jainism),which challenged the religious orthodoxy of the Vedic Period.
Two of the Mahājanapadas were most probably ganatantras and others had forms of monarchy. Ancient Buddhist texts like the Anguttara Nikaya make frequent reference to sixteen great kingdoms and republics which had developed and flourished in a belt stretching from Gandhara in the northwest to Anga in the eastern part of the Indian subcontinent. They included parts of the trans-Vindhyan region, and all had developed prior to the rise of Buddhism in India.
In the later Vedic period, the tribal organisations changed its identity and gradually shifted to the territorial identity, and the area of settlement were now regarded as janapadas or states. In transition from tribe to monarchy, they lost the essential democratic pattern of the tribe but retained the idea of government through an assembly representing the tribes. These states consisted of either a single tribe such as the Shakyas, Kolias, Mallas etc. or a confederacy of tribes such as the Vrijis, Yadavas, Parchala etc.
The people in the lower Ganges Valley and Delta, which were outside the Aryan pale, were regarded as Mlecchas. There was, therefore, a strong consciousness of the pure land of the Aryans called Aryavarta. Each janapada tried to dominate and subjugate other janapadas to become Mahajanapadas. According to Anguttara Nikaya, there were about sixteen Mahajanapadas in the sixth century BC. Their capitals and locations are given in a table on the 16 Mahajanapadas.
The kings in these states had the supreme authority. The Mahajanapadas of Vrijji, Malla, Kuru, Panchal and Kamboj were republican states and so were other smaller states like Lichhavi, Shakya, Koliya, Bhagga, and Moriya. These republican states had a Ganaparishad or an Assembly of senior and responsible citizens. This Gana-Parishad had the supreme authority in the state. All the administrative decisions were taken by this Parishad. Again, the republics were basically of two types: (a) the republics comprising a single tribe like those of the Sakyas, the Kolias and the Mallas, and (b) the republics comprising a number of tribes or the republics of confederacy like the Vrijjis.