Conflicts with Rome

During the 3rd century BC, Southern Italy and Sicily became part of the Roman State, and some Greek cities decided to form alliances with their powerful new neighbour, who would then defend them in their local conflicts.

In 229, Greek cities on the Adriatic Sea and the coastal plains of Epirus were threatened by Illyrian pirates and decided to call on the Roman army to protect them.

But it was the “Macedonian Wars” that really gave Rome a foothold in the region. The Romans made alliances with the small kingdoms that had been created, which were now fighting against the descendants of the diadoci.
 

In the battle of Cynoscephalae in 197, during the 2nd Macedonian War, the Romans crushed the army of Philip V, King of Macedonia. A peace treaty was signed in 196, and the Greek cities were officially pronounced independent, though in fact they came under Roman rule.

In 192, the Seleucid King, Antiochus III, marched on Greece. The Roman Army blocked his march into Greece at Thermopylae, and he returned to Asia Minor. Beaten a second time at Magnesia ad Sipylum, Antiochus was forced to abandon Thrace and a large part of Asia Minor. 

Rome again invaded Greece in 168, defeating the Macedonian army at the Battle of Pydna. The Macedonian monarchy was abolished in 167, and the kingdom came under Roman authority.

In 149, a revolt broke out in Macedonia during the 4th Macedonian War, but this was quickly repressed by Rome, and the region became a Roman province governed by a proconsul whose seat was in Thessalonica. In 146, all Greece came under Roman rule. 

Hellenic civilization continued to spread throughout the Mediterranean Basin, in part thanks to its inclusion in the Roman Empire.