31 BCE
Roman Civil War: Battle of Actium: Off the western coast of Greece, Octavian Caesar defeats naval forces under Mark Antony and Cleopatra VII. Agrippa storms Leucas, giving Octavian an anchorage and a second depot for his land supplies. He seizes the garrison at Patrae, and takes Antony's headquarters. Amyntas, king of Galatia, deserts with 2,000 cavalry to Octavian. One-third of Antony's oarsmen are lost to malnutrition, disease and desertion.
Geopolitics & Diplomacy
- Winter – Octavian (32 years old) takes court at Samos. After his decisive victory at Actium he builds Nicopolis; the city is populated by Greeks from settlements further inland.source
Conflict & Security
- September 2 – Roman Civil War: Battle of Actium: Off the western coast of Greece, Octavian Caesar defeats naval forces under Mark Antony and Cleopatra VII.source
- Antony, alerted by Octavian's presence, sets up camp on the southern shore, at the promontory of Actium. He dispatches a force to isolate the camp of Octavian in the valley of Louros.source
- The Egyptian fleet (60 warships), including Cleopatra's treasure ship, retreats to Taenarus. Antony transfers his flag to a smaller vessel and breaks through Octavian's line.source
- Agrippa storms Leucas, giving Octavian an anchorage and a second depot for his land supplies. He seizes the garrison at Patrae, and takes Antony's headquarters.source
- Amyntas, king of Galatia, deserts with 2,000 cavalry to Octavian. One-third of Antony's oarsmen are lost to malnutrition, disease and desertion.source
Exploration & Expansion
- Octavian crosses the Strait of Otranto and lands with an army (15 legions) at Panormus in Dalmatia. He marches to Toryne in the south, and establishes a bridgehead at the Gulf of Ambracia.source
- Marcus Vipsanius Agrippa sails with 300 war galleys to the western Peloponnese, and occupies strategic positions around the Gulf of Corinth to cut off Antony's line of communication.source
- In the Judean Desert on an isolated rock plateau, fortress Masada is completed. Herod the Great builds an armory, barracks, storehouses and a palace.source
Religion & Belief
- Augustus, then known as Imperator Caesar, becomes Roman Consul for the third time. Antony was designated as his colleague but is deposed from office, an action that Antony does not recognise. Elected in Antony's place is Marcus Valerius Messalla Corvinus; Antony's consulship is not recorded in some sources, as Valerius is marked instead as consul ordinarius.source
Science & Discovery
- The Hellenistic period ends (or AD 14 by some scholars).source
Climate & Environment
- 31 BC Judea earthquake, earthquake mentioned in catalogues of historical earthquakes. It affected the Herodian Kingdom of Judea in the Holy Land.source