Mark Antony's commitment of Roman resources to Egypt and Cleoparta VII ensured a showdown with his 
rival triumvir Octavian. While Antony's fortunes in Rome were in decline, the 32-year old Octavian had been steadily winning popular favor by substituting moderation and mercy for earlier cruelties. In May 32 B.C. Antony formally divorced Octavian sister Octavia. Octavian then publicized Antony's will, which deed various woman possessions to the children of his affair with Cleopatra. Roman sentiment became so outraged that Octavian was directed to make war on Egypt.Early in 31 B.C. Octavian landed an army of 40,000 men in Epirus, on the west coast of Greece. Just to the south, in the Ambracian Gulf, stood Antony's Roman-Egyptian fleet. On the promontory of Actium, on the south side of the Gulf, stood Antony's army, numberin also about 40,000 men. For months the two antagonist eyed each other without giving battle. During this time however, Octavian's ship cut Antony's supply line from the Pelopennesus back to Egypt. Finally, at dawn on September 2, 31 B.C. Antony risked everything on a naval battle. With superiority in numbers (480 against slightly more than 400) and in the size of its warshisp, the Roman-Egyptian navy sailed into the Ionean sea, seeking an early advantage over the lighter Liburnian (two banks of oars) vessels of Octavian. Octavian himself commanded the right squadron, Marcus Octavius the center, C. Sosius the left. Cleopatra's squadron stood in the rear, to the right of center. Opposing this formation were the three enemy squadrons commanded by, from left to right, Marcus Vipsanius Agrippa, Arruntius, Octavian.
Each side tried to turn the opponents's northern flank. In the afternoon Antony's center and left began giving away. Cleopatra then sailed her 60 Egyptian ships between the two struggling armadas and left the scene of battle. Antony transferred to a quinquerreme (five banks of oars) and followed, boarding the Egyptian flagship Antonia farther out in the Ionian sea. The leaderless Antonian navy was now hopelesssly beaten. Octavian's swifter Liburnians, dodging the rams and missiles of the heavier vessels, methodically set fire to the opposing warships. At the end of ten hours of fighting the survivors of Antony's burning fleet surrendered. Five thousand of his men were dead.
On the land the flight of Antony caused equal consternation among the troops. They became even more frustrated when their leader, P. Crassus Canidius, fled to Egypt also. Octavian refused to attack them. Each day desertions increased. By September 9 the entire army melted away.
In Rome popular clamor force Octavian to launch an invasion of Egypt the following year. He arrived at Alexandria on August 1, 30 B.C. The still powerfull army (11 legions) Antony had stationed to defend Egypt promptly deserted to the enemy. Antony and then Cleopatra committed suicide. Octavian looted the Ptolemaic treasures, exacted tribute, and returned to Rome as sole master of western world. Three years later the senate conferred upon him the title "agustus" (exalted). As such he became the first ruler of the Roman Empire that was to endure for the next 500 years. The battle of Actium had determined that europe's cultural axis would not be turned toward the east.