The genealogy and chronology of the Saisunagas are not clear. Saisunaga defeated the king of Avanti which was made part of the Magadhan Empire. After Saisunaga, the mighty empire began to collapse. His successor was Kakavarman or Kalasoka.
During his reign the second Buddhist Council was held at Vaisali. Kalasoka was killed by the founder of the Nanda dynasty.
The fame of Magadha scaled new heights under the Nanda dynasty. Their conquests went beyond the boundaries of the Gangetic basin and in North India they carved a well-knit and vast empire.
Mahapadma Nanda was a powerful ruler of the Nanda dynasty. He uprooted the kshatriya dynasties in north India and assumed the title ekarat. The Puranas speak of the extensive conquests made by Mahapadma. The Hathigumpha inscription of Kharavela of Kalinga refers to the conquest of Kalinga by the Nandas. Many historians believe that a considerable portion of the Deccan was also under the control of the Nandas. Therefore, Mahapadma Nanda may be regarded as a great empire builder.
According to the Buddhist tradition, Mahapadma Nanda ruled about ten years. He was succeeded by his eight sons, who ruled successively. The last Nanda ruler was Dhana Nanda. He kept the Magadhan empire intact and possessed a powerful army and enormous wealth. The fabulous wealth of the Nandas is also mentioned by several sources. The enormous wealth of the Nandas is also referred to in the Tamil Sangam work Ahananuru by the poet Mamulanar. The flourishing state of agriculture in the Nanda dominions and the general prosperity of the country must have brought to the royal treasury enormous revenue. The oppressive way of tax collection by Dhana Nanda was resented by the people. Taking advantage of this, Chandragupta Maurya and Kautilya initiated a popular movement against the Nanda rule. It was during this time that Alexander invaded India.