Nanda Empire
In the Greco-Roman world, accounts of the Gangaridai Kingdom are considered by historians to have referred to Bengal. At the time of Alexander the Great's invasion of India, the collective might of the Gangaridai and the Nanda Empire (Bihar) deterred the Greek army. The Gangaridai army was stated to have a war elephant cavalry of 6000 elephants. The archaeological sites of Wari-Bateshwar and Chandraketugarh are linked to the Gangaridai kingdom.