Mountainous northern isolation saw Thessaly regarded as ‘semi-Hellenized’, with its own separate, stratified society that was considered decades behind Greece developmentally. Geography also endowed the region with the largest stretches of grassland in Greece, enabling it to produce grain for export and horses, with Thessalian cavalry considered Greece's best.
Rich and populous, Thessaly's potential was ruined by internal divisions. The area was divided into four administrative regions called tetrads: Pelasgiotis, Phthiotis, Thessaliotis, and Histiaeotis, dominated by aristocratic landowners. The Thessalian polity also incorporated surrounding peoples in Perrhaebia, Magnesia, Achaea, Dolopia, Ainis, Malis, and Oetaea as subordinate perioeci (“dwellers around”). There was also a subjugated underclass called the penestae, who may have had a role similar to the Spartan helots.
The history of these social and political developments is uncertain: the latter came from an archaic migration by western tribes, while tradition credits a certain Aleuas with the tetrarchic division. These tetrads formed the basis for the position of tagus (also called ‘king’ or ‘archon’), elected in times of crisis with the power to call an army of all Thessaly (cf. Xenophon, Hellenica 6.1.8–9, 19).
However, if these tetrarchic reforms were introduced at some point in the sixth or fifth century, they had little impact on Thessalian power or unity; if anything, that power declined. The Athenian orator Isocrates queried why, despite their wealth and cavalry, the Thessalians were so incapable of protecting their borders – he blamed it on arrogance and insolence (Isocrates, 117), but a “lack of strong central government and the weakness of the federal institutions” seems more likely (Sprawski, 204).
