I just was about to read a fact that, there had been a great war planned against Tamizh Naadu by Ashoka the great ( Not directly, but by one of his commanders ). He had overcome Kudamalainaadu after a massive fight. Maurya Army seems to have lost the confidence of winning the Tamizhnaadu.
And hence settled in Kudamalai naadu to prepare for the war. When he marched forward. The entire Thamizhnaadu joined together under Chola Kochengatchenni and drove them beyond Kudamalai naadu.
And thus Ashoka, gave up the plans of annexing the other kingdoms.