This era sees the inception of the Greco-Roman world, in which the Roman Republic dominates the eastern Mediterranean Basin.

Rome, victorious in its war against Seleucid king Antiochus III,  punishes its opponents, the Aetolians, and rewards its supporters, notably Pergamon and Rhodes, which are granted new territories, including Greek cities, at the expense of Rome’s stated policy, "the liberation of the Greeks".

The Spartans attack Las, near Gythium, in 189 BCE.

Philopœmon, strategos of the Achaean League, threatens war unless Sparta delivers those responsible for the action.

When the Spartans respond by killing thirty pro-Achaean citizens, voting to secede from the League, and surrendering to Roman protection, Philopœmon declares war.

Philopoemen had taken advantage of the Aetolian treachery towards Sparta and had entered the city with his Achaean army.

Now in full control of Sparta, Philopoemen has forced Sparta to become a member state of the Achaean League.

Sparta's entry to the League had raised the problem of how to deal with the all the Spartans exiled by the social-revolutionary regimes that had dominated Sparta for a number of years.

Philopoemen had wanted to restore only those Spartans who were willing to support the League.

This meant that he has adopted an uncompromising hostility to traditional Spartan concerns.

When an infringement of the Achaean League’s promise to Sparta prompts the Spartans to secede from the confederation in 188, Philopoemen enters northern Laconia with his army and a group of Spartan exiles.

Capturing between eighty and three hundred and fifty members of the Spartan secessionist movement, he executes them after a show trial.

His army demolishes the wall that the former tyrant of Sparta, Nabis, had built around the city, and mandates the exile of all mercenaries, anti-Achaeans, and enfranchised helots.

Philopoemen now restores Spartan citizenship to the exiles and abolishes Spartan law and its education system, introducing Achaean law and institutions in their place.

Sparta's role as a major power in Greece ends, while the Achaean League becomes the dominant power throughout the Peloponnese.

The Roman Senate hears complaints from the Spartans, but takes no immediate action against the Achaeans.

The continuing quarrels among the Greek cities and leagues increases the conviction in Rome that there will be no peace in Greece until Rome takes full control.