The breach between Antony and Octavian prompted a large portion of the Senators, as well as both of that year’s consuls, to leave Rome and defect to Antony. However, Octavian received two key deserters from Antony in the autumn of 32 BC: Munatius Plancus and Marcus Titius. These defectors gave Octavian the information that he needed to confirm with the Senate all the accusations that he made against Antony.
Octavian forcibly entered the temple of the Vestal Virgins and seized Antony’s secret will, which he promptly publicized. The will would have given away Roman-conquered territories as kingdoms for his sons to rule, and designated Alexandria as the site for a tomb for him and his queen. In late 32 BC, the Senate officially revoked Antony’s powers as consul and declared war on Cleopatra’s regime in Egypt.
In early 31 BC, Antony and Cleopatra were temporarily stationed in Greece when Octavian gained a preliminary victory: the navy successfully ferried troops across the Adriatic Sea under the command of Agrippa. Agrippa cut off Antony and Cleopatra’s main force from their supply routes at sea, while Octavian landed on the mainland opposite the island of Corcyra (modern Corfu) and marched south. Trapped on land and sea, deserters of Antony’s army fled to Octavian’s side daily while Octavian’s forces were comfortable enough to make preparations.
Antony’s fleet sailed through the bay of Actium on the western coast of Greece in a desperate attempt to break free of the naval blockade. It was there that Antony’s fleet faced the much larger fleet of smaller, more maneuverable ships under commanders Agrippa and Gaius Sosius in the Battle of Actium on 2 September 31 BC. Antony and his remaining forces were spared only due to a last-ditch effort by Cleopatra’s fleet that had been waiting nearby.
Octavian pursued them and defeated their forces in Alexandria on 1 August 30 BC—after which Antony and Cleopatra committed suicide. Antony fell on his own sword and was taken by his soldiers back to Alexandria where he died in Cleopatra’s arms. Cleopatra died soon after, reputedly by the venomous bite of an asp or by poison. Octavian had exploited his position as Caesar‘s heir to further his own political career, and he was well aware of the dangers in allowing another person to do the same. He therefore followed the advice of Arius Didymus that “two Caesars are one too many”, ordering Caesarion, Julius Caesar‘s son by Cleopatra, killed, while sparing Cleopatra’s children by Antony, with the exception of Antony’s older son. Octavian had previously shown little mercy to surrendered enemies and acted in ways that had proven unpopular with the Roman people, yet he was given credit for pardoning many of his opponents after the Battle of Actium.
After Actium and the defeat of Antony and Cleopatra, Octavian was in a position to rule the entire Republic under an unofficial principate —but he had to achieve this through incremental power gains. He did so by courting the Senate and the people while upholding the republican traditions of Rome, appearing that he was not aspiring to dictatorship or monarchy. Marching into Rome, Octavian and Marcus Agrippa were elected as dual consuls by the Senate.
Years of civil war had left Rome in a state of near lawlessness, but the Republic was not prepared to accept the control of Octavian as a despot. At the same time, Octavian could not simply give up his authority without risking further civil wars among the Roman generals and, even if he desired no position of authority whatsoever, his position demanded that he look to the well-being of the city of Rome and the Roman provinces. Octavian’s aims from this point forward were to return Rome to a state of stability, traditional legality, and civility by lifting the overt political pressure imposed on the courts of law and ensuring free elections—in name at least.