(1) During the 6th and 4th centuries BC, Magadha (in present-day Bihar) became the most powerful Mahajanapada. Modern historians explain this in a variety of ways : ● It was a region where agriculture was especially productive. ● Besides, iron mines (in present-day Jharkhand), were accessible and provided resources for tools and weapons. ● Elephants, an important component of the army, were found in forest in the region. ● Moreover, the Ganga and its tributaries provided a means of cheap and convenient communication.