Out of the sixteen Mahajanapadas four were very powerful. They were Magadha, Vatsa, Avanti and Koshala.The period from 4th century to 6th century BC saw the struggle for supremacy among these four Mahajanapadas.Magadha emerged as the powerful and prosperous state .
The founder of Magadha was Jarasandha and Brihadratha.But the growth started under the Haryanka, expansion took place under the Shishunaga and Nanda, reached its zenith under the Mauryas.The earliest capital of Magadha was at Rajgir which was called Girivraja at that time. The main reasons for the rise of Magadha was the geographical location with both Rajgir and Pataliputra situated at strategic locations. Abundance of natural resources such as iron enabled Magadhan rulers to equip with sufficient and effective weapons. Rise of the town and use of metallic money boosted trade and commerce. The princes could levy tolls and taxes to maintain their armies. The rulers started using elephants in the warfare against the enemies.