Octavian Defeats Antony and Cleopatra at Actium

On 2 September 31 BC, the naval forces of Octavian confronted the joint fleet of Mark Antony and Queen Cleopatra VII of Egypt off the promontory of Actium in northwestern Greece. The engagement served as the decisive military encounter in a protracted struggle between the two surviving leaders of the Second Triumvirate, an alliance that had officially expired at the end of 33 BC. Octavian's operational commander, Marcus Vipsanius Agrippa, had already seized key coastal bases and blockaded Antony's logistical routes across the Peloponnese, trapping his adversary's army and ships in the Ambracian Gulf.

The bitter rivalry traced directly back to the turmoil after the assassination of Julius Caesar in 44 BC. Octavian drew his authority and soldierly support from Caesar's testament, which named him the dictator's adopted son and primary heir. Antony, formerly Caesar's senior lieutenant, maintained an independent standing with the Roman legions and subsequently allied with Cleopatra. Their public elevation of Caesarion, the disputed son of Caesar and Cleopatra, challenged Octavian's sole claim to Caesar's legacy. Octavian capitalised on Antony's abandonment of his Roman wife, Octavian's sister Octavia, and publicised Antony's will to persuade the Senate to strip Antony of his consulship and declare war against Cleopatra.