The whole of Italy of its own accord took an oath of allegiance to me and demanded that I should be its leader in the war which I won at Actium -
Res Gestae of Augustus.
The site of the final battle between Octavian (no longer Octavius, not yet Augustus) and the combined forces of Cleopatra and Marc Antony.
After Caesar's death in 44 B.C., two men struggled for control of Rome: the young Gaius Octavius, Julius Caesar's adopted son, and Marcus Antonius, his former military commander (there was also a third in the second triumvirate, Marcus Lepidus, but he was never really a contender). The treaty of Brundisium divided the empire into three sections; the East would be controlled by Marc Antony, Italy and lower Gaul by Octavian, and northern Africa by Lepidus. All three, of course, began a propaganda campaign, declaring themselves the true saviours of Rome. While Marc Antony was galloping across the east, winning minor victories over pirates and cheating on his wife, Octavian's sister, with Cleopatra, Octavian spread devastating rumours about Antony's reckless, eastern behaviour and foreign pollution. Antony's support in Rome slowly dwindled, so that by 31 B.C., the battle could easily be painted as a war between Rome and some evil foreigners instead of a true civil war.
The battle between the two finally came to a head at Actium in September of 31 B.C.; Octavian's fleet, under the command of Marcus Agrippa, sailed out to meet the planned invasion fleet of Egypt off the coast of Greece.
The site is really a set of facing promontories guarding the Ambracian Gulf. At the time, there was little there besides the wilderness and a lone temple of Apollo on the southern promontory on which Marc Antony had encamped his forces.
The battle, though one of the largest naval engagements in the ancient world, was soon over. Four days of delay ended in a single day of combat, during which Octavian's fleet, though smaller and outclassed, rounded up the hulking boats of Antony in the narrow, cramped bay and destroyed them. Cleopatra and Marc Antony escaped in her flagship, fleeing before the battle was even finished.
After the battle, Octavian built a large memorial, consisting of the beaks of the Egyptian galleons, set in the stone cliffs (the notches are still visible today), below which he built a small "victory city", Nicopolis, and held celebrations for several weeks.
Of course, Octavian eventually followed to Egypt, where Antony and Cleopatra had already died, and swallowed the Egyptian lands into the expanding Roman empire. The details of that belong elsewhere.
Actium soon became a rallying point of propaganda for Octavian. He declared that he won a great victory for Roman liberty by crushing not Antony, but the mad bitch-tyrant Cleopatra. Finally, with the threats to the Republic destroyed, he could begin a true era of peace and prosperity, the pax Augusta.
Literature was not to be left out by the great war; Vergil inserted some intricate descriptions of the Great Augustus and his victory for freedom everywhere. Perhaps the most memorable is still Horace Ode I.37, which begins:
Now we get drunk, now pound the ground
with dancing, now's the time to deck
the couches of the gods with sumptuous
feasts, my comrades.
Before, who would have thought to break
the good wines from the ancient cellars,
while some mad bitch plotted
ruin for the empire,
With her disgusting flock of followers,
diseased and tainted, hoping in vain
for something, anything, drunk
on power...