The political history of the Tamils covers a period of five centuries (so far as we certainly know) from the second century BC to the end of the second century AD.
This may be treated as the true Sangam period and not merely the first 2 or 3 centuries of the Christian era as Vincent Smith said or a longer period of a thousand years from fifth century B.C. to the fifth century AD as V.R. Ramachandra Dikshitar thought.
We have positive proof for the provenance and occurrence of the events of the Sangam age for a more delimited period of five centuries only. To restrict this period to the first three centuries of the Christian era will be to forget the Asokan mention of the Pandyan kingdom, of Kharavela’s reference to the Tamil confederacy and the probable resistance of this confederacy to Bindusara and its certain defeat of Satakarni II and also the fact that the well developed polity we find in the early centuries of the Christian era must have had roots going down at least by two or three centuries BC.
We shall now make a survey of the political history of the three dynasties during the Sangam period with the help of mainly the Sangam literature and secondarily external sources like epigraphs found outside the Tamil country and foreign notices of Tamilaham of the Sangam age. We shall take up the history of the Cheras first, since the earliest credible political happennings of the Tamil country belong to them.