First, let's start with some facts that everybody with a little knowledge of history should know. The Roman Empire was the greatest empire that ever existed, and probably the greatest empire that ever will be. It was the Romans that first had the idea of being a republic.
The Battle of Actium was the last battle in which the Roman Republic used its navy, probably just as well because they didn't have real reasons to be proud of their navy. The first couple wars in which the Romans used its navy proved to be disastrous.
Compare that to the fact that the Roman Empire had the greatest army the world had ever seen, Rome struggled along with its crippled navy until a grappling engine was invented that made it possible for the Roman soldiers to board the enemy ships.
Things were looking up, now they did not have to really fight that much with the navy, all they had to do was to get their ships close enough to get the men on the shore. Then the army would do the rest.
This system took some time to develop and it didn't really get going until Rome's final naval battles were fought. The Battle of Actium is one of the last and the above strategy was employed during the sea battles. The navy started to degrade towards the end of the Roman Empire but during this battle it was at the height of its power and strength.
It was actually a civil war, there was the side that supported Mark Antony and there was the side that supported Octavian, this war was fought during September in the year 31 BC, and it was fought next to a Roman Colony near Greece.
Octavian was the adopted son of Caesar, the problem started when Caesar had a baby with Cleopatra named Caesarion, this was pressure enough but then Mark Antony decided that Caesarion was the rightful heir and he declared this in a nice loud voice.
This started a lot of fighting in the senate but in the end, they stripped Mark Antony of his power and sent him on his way, at the same time declaring war on Cleopatra.
Mark Antony had lost the war before he ever began fighting; while Antony was waiting for Octavian to arrive at the gulf of Actium, there was a malaria outbreak aboard the ships that killed a lot of oarsman.
That with the fact that the supply lines had been cut, Antony was left with a severely demoralized crew, not to mention that he was undermanned and the type of ships he had, demanded a big crew to successfully maneuver.
When Octavian arrived, he had fresh crews and small light ships that were easier to maneuver compared to the huge ships that Antony had. As the battle progressed, Antony's general Delius defected to the other side taking the battle plans with him.
Things only got worse from there. Eventually Antony had to leave the protection of the shoreline and go after Octavian because his ships would constantly stay out of range.
The battle was being lost however, and when Cleopatra saw this, she decided that she did not want to stick around and see, so she retreated. When Mark Antony realized this, he too got on a small ship and managed to escape, abandoning his entire fleet to certain death.
Because of the defeat at Actium, over half of Antony's army later on deserted him, leaving him with almost no one to fight for him. This coupled with the fact that a mix-up in communication left Antony with the belief that Cleopatra had been killed pushed Antony to the point of committing suicide.
When Cleopatra got the news, she too committed suicide so as not to be paraded in the streets of Rome as a sign of Octavian's victory. The war was won and Octavian was named the first citizen of Rome. Rome was no longer a republic but an Empire....