you seems like dravidian nationalist, what southern kingdoms are you even talking about? the ones mentioned by ashoka in the first place? or the ones conquered by the mauryas, wasn't andhra, karnataka under mauryas who gave birth to ninety percent southern kingdoms in the first place including satavahanas, chalukyas, vijayanagar. pallavas etc? kalingas did have a very strong military and they operated four gigantic forts, the remains of which can still be seen today, and they had a really big trade network in SEA.