There was a striking contrast in the types of ships in the opposing ranks. The galleys of Octavius were low in the water, and nimble in their handling; those of Antony were bulky and high, with five to ten banks of oars, and their natural unhandiness was made worse by a device intended to protect them against ramming. This consisted of a kind of boom of heavy timbers rigged out on all sides of the hull. In addition to the higher sides these ships supported towers and citadels built upon their decks, equipped with every form of the artillery of that day, especially catapults capable of hurling heavy stones upon the enemy's deck.

Against such formidable floating castles, the light ships of Agrippa and Octavius could adopt only skirmishing tactics. They rushed in where they could shear away the oar blades of an enemy without getting caught by the great grappling irons swung out from his decks. They kept clear of the heavy stones from the catapults through superior speed and ability to maneuver quickly, but they were unable to strike their ponderous adversaries any vital blow. On the other hand the great hulks of Antony were unable to close with them, and though the air was filled with a storm of arrows, stones and javelins, neither side was able to strike decisively at the other. As at Salamis the opposite shores were lined with the opposing armies, and every small success was hailed by shouts from a hundred thousand throats on the one side and long drawn murmurs of dismay from an equal host on the other.

In these waters a north wind springs up every afternoon—a fact that Antony and Cleopatra had counted on—and as soon as the breeze shifted the royal galley of Cleopatra spread its crimson sail and, followed by the entire Egyptian division, sailed through the lines and headed south. Antony immediately left his flagship, boarded a quinquereme and followed. This contemptible desertion of the commander in chief was not generally known in his fleet; as for the disappearance of the Egyptian squadron, it was doubtless regarded as a good riddance. The battle, therefore, went on as stubbornly as ever.

Late in the afternoon Agrippa, despairing of harming his enemy by ordinary tactics, achieved considerable success by the use of javelins wrapped in burning tow, and fire rafts that were set drifting upon the clumsy hulks which could not get out of their way. By this means a number of Antony's ships were destroyed, but the contest remained indecisive. At sunset Antony's fleet retired in some disorder to their anchorage in the gulf. Octavius attempted no pursuit but kept the sea all night, fearing a surprise attack or an attempted flight from the gulf.

Meanwhile a flying wing of Octavius's fleet had been sent in pursuit of Antony and Cleopatra, who escaped only after a rear guard action had been fought in which two of Cleopatra's ships were captured. The fugitives put ashore at Cape Tænarus, to enable Antony to send a message to his general, Canidius, ordering him to take his army through Macedonia into Asia. Then the flight was resumed to Alexandria.

On the morning of the 3d Octavius sent a message to the enemy's camp announcing the fact of Antony's desertion and calling on the fleet and army to surrender. The Roman soldiers were unwilling to believe that their commander had been guilty of desertion, and were confident that he had been summoned away on important business connected with the campaign. Their general, however, did not dare convey to them Antony's orders because they would betray the truth and provoke mutiny. Consequently he did nothing. Certain Roman senators and eastern princes saw the light and quietly went over to the camp of Octavius. Several days of inaction followed, during which the desertions continued and the rumor of Antony's flight found increasing belief. On the seventh day, Canidius, who found himself in a hopeless dilemma, also went over to Octavius. This desertion by the commander settled the rest of the force. A few scattered into Macedonia, but the great bulk of the army and all that was left of the fleet surrendered. Nineteen legions and more than ten thousand cavalry thus came over to Octavius and took service under him. This was the real victory of Actium. In the words of the Italian historian Ferrero, "it was a victory gained without fighting, and Antony was defeated in this supreme struggle, not by the valor of his adversary or by his own defective strategy or tactics, but by the hopeless inconsistency of his double-faced policy, which, while professing to be republican and Roman, was actually Egyptian and monarchical."

The story of the naval battle of Actium is a baffling problem to reconstruct on account of the wide divergence in the accounts. For instance, the actual number of ships engaged is a matter of choice between the extremes of 200 to 500 on a side. And the consequences were so important to Octavius and to Rome that the accounts were naturally adorned afterwards with the most glowing colors. Every poet who lived by the bounty of Augustus in later years naturally felt inspired to pay tribute to it in verse. But the actual naval battle seems to have been of an indecisive character. For that matter, even after the wholesale surrender of Antony's Roman army and fleet, neither Anthony nor Octavius realized the importance of what had happened. Antony had recovered from worse disasters before, and felt secure in Alexandria. Octavius at first followed up his advantage with timid and uncertain steps. Only after the way was made easy by the hasty submission of the Asiatic princes and the wave of popularity and enthusiasm that was raised in Rome by the news of the victory, did Octavius press the issue to Egypt itself. There the war came to an end with the suicide of both Antony and Cleopatra.

As in the case of the indecisive naval battle off the capes of the Chesapeake, which led directly to the surrender of Cornwallis, an action indecisive in character may be most decisive in results. Actium may not have been a pronounced naval victory but it had tremendous consequences. As at Salamis, East and West met for the supremacy of the western world, and the East was beaten back. It is not likely that the Egyptian or the Syrian would have dominated the genius of the western world for any length of time, but the defeat of Octavius would have meant a hybrid empire which would have fallen to pieces like the empire of Alexander, leaving western Europe split into a number of petty states. On the other hand, Octavius was enabled to build on the consequences of Actium the great outlines of the Roman empire, the influence of which on the civilized world to-day is still incalculable. When he left Rome to fight Antony, the government was bankrupt and the people torn with faction. When he returned he brought the vast treasure of Egypt and found a people united to support him. Actium, therefore, is properly taken as the significant date for the beginning of the Roman empire. Octavius took the name of his grand-uncle Cæsar, the title of Augustus, and as "Imperator" became the first of the Roman emperors.

The relation of the battle of Actium to this portentous change in the fortunes of Octavius was formally recognized by him on the scene where it took place. Nicopolis, the City of Victory, was founded upon the site of his camp, with the beaks of the captured ships as trophies adorning its forum. The little temple of Apollo on the point of Actium he rebuilt on an imposing scale and instituted there in honor of his victory the "Actian games," which were held thereafter for two hundred years.

After the battle of Actium and the establishment of a powerful Roman empire without a rival in the world, there follows a long period in which the Mediterranean, and indeed all the waterways known to the civilized nations, belonged without challenge to the galleys of Rome. Naval stations were established to assist in the one activity left to ships of war, the pursuit of pirates, but otherwise there was little or nothing to do. And during this long period, indeed, down to the Middle Ages, practically nothing is known of the development in naval types until the emergence of the low, one- or two-banked galley of the wars between the Christian and the Mohammedan. The first definite description we have of warships after the period of Actium comes at the end of the ninth century.