The so-called Achaean War, which broke out in 146 between the Romans and the Achaean League (in the Peloponnese) with almost all of Boeotia, is an event of great significance, but one which until recently no one supposed might have affected Eretria at all. The Greek forces were ruthlessly put down by the consul Lucius Mummius, who ordered the complete destruction of the city of Corinth. It has long been known that the people of Chalkis joined in this insurrection against Roman power and were cruelly punished for doing so. But the Eretrians?
A modest inscription -a simple proclamation of the victors in an athletic event at the stadium- attests that a competition was held in honor of the redoubtable Mummius, associated with the great Artemis Amarysia. This document incontestably proves that the Eretrians worshiped the Roman consul, whom they considered their benefactor. We can infer from it that in the war they must have adopted an attitude diametrically opposed to that of their immediate neighbors; this support for Rome becomes clear when we learn that they had very shortly before been the victims of the aggressive policies of the Boeotians of Thebes. Almost alone among the Greeks to have sided with Mummius, they must have obtained from the consul, once he was victorious, some substantial reward. But what was it?
The most likely hypothesis - no more than a conjecture based on various clues- is that they were given the territory of Oropos, which they had always coveted, and from which they were most likely able to benefit starting in 146. This would explain the relative wealth that at least part of Eretrian society seems to have enjoyed at that time. Several inscriptions regarding the activities of the ephebes, their trainers, and their professors in the Gymnasium testify to this; they also reveal to us the existence of a certain plutocratic "bourgeoisie," from which originated the notables who erected statues to members of their families. Half a century later, having taken the wrong side in the war against King Mithridates of Pontos in 87-86, the Eretrians lost not only this precious continental possession, but also their privileged status. And from this severe blow the Eretrians were never again entirely to recover.