Here is some info on the history of Ancient Athens during the time that Epicurus was alive.
Wikipedia says Epicurus lived 341-270BC. Diogenes Laertius says 341-271BC.
The following short section is from Wikipedia:
Hellenistic Athens
Further information: Hellenistic Greece, Lamian War, Phocion, Demetrius of Phalerum, Chremonidean War, Second Macedonian War, First Mithridatic War, Lycurgus of Athens, Antigonid dynasty, and Seleucid Empire
Shortly after the death of Alexander the Great, Antipater and Craterus became joint generals of Greece and Macedonia.[21] Athens joined Aetolia and Thessaly in facing their power, known as the Lamian War.[22] Craterus fell in a battle against Eumenes in 320 BC,[23] leaving Antipater alone to rule for a year, till his death in 319 BC.[24] Athens had a central role in the struggle for his succession, when Antipater's son, Cassander, secured the Piraeus leaving Athens without a source of supplies,[21] to contest Antipeter's successor, Polyperchon. To consolidate power against Cassander, Polyperchon restored Athens's democracy, as it was before the Lamian War. However, after losing the fleet one year prior, Polyperchon had to flee Macedon when in 316 BC Cassander secured control of Athens. Cassander appointed Demetrius of Phalerum as head of the administration of Athens. Demetrius remained in power until 307 BC when Cassander's enemy, Demetrius Poliorcetes captured Athens,[25] and Macedon, ending the short-lived Antipatrid dynasty and installing his own.
Athens and the rise of the Roman empire
After the Pyrrhic War (280–275 BC) Rome asserted its hegemony over Magna Grecia and became increasingly involved in Greece and the Balkans peninsula.