Modern studies have emphasized the contradictory nature of the ancient traditions concerning the aftermath of the Battle of Sepeia (494 BC), in which the Argive army was destroyed by the Spartans. This article tackles the most significant point of agreement in these traditions: the theme of Argive ‘oligandry’, the demographic crisis caused by the battle. An analysis conducted on the basis of Ansley J. Coale and Paul Demeny’s Model Life Tables shows that the real impact of the demographic crisis was felt in the age structure of Argos’ population rather than in the sheer size of its citizen body. Consequently, this article argues that the political ramifications of the battle originated not from the demographic crisis alleged by the tradition, but from the state of powerlessness and regional isolation into which Argos was plunged by the defeat of 494. This argument, which supports a reappraisal of Plutarch’s (De mul. vir. 4) version of Argos’ response to Sepeia, also helps explain why Argos embraced a markedly aggressive foreign policy towards the towns of the plain in the following decades.