asitaraman said"Actually, it was a confederation of South Indian kings who stood up to Bhimbisara. Bhimbisara claims to have received tributes and stopped his campaign and his inscriptions extend only up to Northern Karnataka the traditional border of Tamizhagam (Thungabadra). South Indian kings that they stopped the king's advamce. There are no records whether a battle actually took place. "

dear asitaraman,
glad people are much interested in Ancient Tamil history.
Sir, as you noted it was king Bhimbhisara planning to conquer south India.
Till that time the extent of Mauryan empire was the river Krishna, and around 272 b.c.e. he sent troops to invade the Tamizh land south of Krishna river.
from ka.appathuraiyaar the Tamizh academician,
Actually a series of battles took place :
1st the Mauryan army attacked a weak Kadamba kingdom at its capital PAAZHI WHICH WAS A FORTIFIED CITY IN THE PRESENT GOA STATE fram and with the help of THE KOSARS the tribalpeople of Rivers Malprabha,Gatprabha and upper Krishna , the border area between Kadamba and mauryan empire. with their help from their Kolhapur town they attacked PAAZHI and captured the whole of Kadamba and its many fort cities .
then the Mauryans and their kosar affliates entered the Tamil naadu through the kaviri-kudhirai malai pass which is the present anthiyur-nallur path.