Pradyota assents the throne of Avanti ending the Brhadratha Dynasty and commencing the Pradyota Dynasty of Magadha. The Mahavamsa states that Ajatasattu's son Udayabhadra succeeded Ajatasattu and ruled for the next sixteen years. He moved his capital to the bank of Ganges which was known as Pataliputra. The succession was followed by Udayabhadra's son Anuruddha and his son Munda in the same family tradition by slaying the father. Munda's son Nagadasaka slew his father and continued reigning through this dynasty of parricides'. The citizens angered by the rule of Haryankas, revolted against Nagadasaka and anointed Shishunaga as the king.
The political process in India started with semi-nomadic tribal units called janas which coalesced into janapadas. The first Vedic realm mentioned in the Vedas is Videha, but its existence mostly falls into the category of the religious-legendary. During the 6th century BCE, the janapadas had formed larger political entities, possibly through a process not unlike the Greek synoecism, in which smaller settlements combined to form city-states with their hinterlands (mahajanapadas). Among the mahajanapadas five cities gained special importance: Rajagriha or Rajgir in Magadha (modern Bihar), Varanasi (formerly called Benares) in Kasi, Kausambi in Vatsa, Sravasti in Kosala, and Champa in Anga. All of these states were in the Gangetic plain of northern India. Other important centers were Ujjain in Avanti and Taxila in Gandhara (today part of Pakistan).
Magadha was mentioned in both the Ramayana and the Mahabharata. The four strongest states - Kasi, Kosala, Magadha and Vrjji - were all along the Ganges River. Of those four, Magadha had several advantages that would help it to prevail in the struggle for supremacy. It has risen to power during the reigns of Bimbisara (544 - 491 BCE) and his son Ajatashatru (491 - 460 BCE). Bimbisara whose city of Rajagriha (modern Rajgir, near Gaya, Bihar) controlled nearby iron-mines. Bimbisara established dynastic relations by intermarriage with the nobility of neighbouring Kosala and Vrijji, and easily dominated the territory of Vanga to the southeast. He was, however, murdered by his son Ajatashatru in 493 BC, who established a fort at Pataliputra (Patna), by the Ganga and near to her confluence with the Gandaki, Sona, and Ganghara Rivers. Ajatashatru was also murdered (461 BC) by his impatient heir and so too, the next five generations.
Magadha expanded to include most of Bihar and much of Bengal with the conquest of Anga, and then expanded up the Ganges valley annexing Kosala and Kashi. Magadha formed one of the sixteen so-called Mahajanapadas. The Magadha empire included republican communities such as Rajakumara. Villages had their own assemblies under their local chiefs called Gramakas. Their administrations were divided into executive, judicial, and military functions. Bimbisara was friendly to both Jainism and Buddhism and suspended tolls at the river ferries for all ascetics after the Buddha was once stopped at the Ganges River for lack of money.
Magadha battled with all of its neighbours, and used its superior weaponry (e.g. the terrible Rathamushala, an armored chariot with fixed iron blades for mowing down opposing forces) to great effect. After the death of Udayan, the kingdom of Magadh declined rapidly and was replaced by the Shishunaga dynasty, which took over in 413 BC. However, the Shishunaga dynasty did not last for more than 50 years and the Nanda dynasty took over.