– Octavian and Mark Anthony, also fought a civil war with Caesar's assassins (Senators Brutus, Cassius, etc.). Octavian and Mark Anthony eventually fought another civil war between themselves to determine the sole ruler of Rome. Octavian emerged victorious and Rome was turned into an empire with a huge standing army of professional soldiers. By the time of Marcus Aurelius, the Romans had expanded to the Atlantic Ocean in the west and to Mesopotamia in the east and controlled Northern Africa and Central Europe up to the Black Sea. However, Aurelius marked the end of the Five Good Emperors, and Rome quickly fell into decline. The Huns, Goths, and other barbaric groups invaded Rome, which continued to suffer from inflation and other internal strifes. Despite the attempts of Diocletian, Constantine I, and Theodosius I, western Rome collapsed and was eventually conquered in 476. The Byzantine empire continued to prosper, however. Medieval warfare When stirrups came into use some time during the Dark Ages militaries were forever changed. This invention coupled with technological, cultural, and social developments had forced a dramatic transformation in the character of warfare from antiquity, changing military tactics and the role of cavalry and artillery. Similar patterns of warfare existed in other parts of the world. In China around the 5th century armies moved from massed infantry to cavalry based forces, copying the steppe nomads. The Middle East and North Africa used similar, if often more advanced, technologies than Europe. In Japan the Medieval warfare period is considered by many to have stretched into the 19th century. In Africa along the Sahel and Sudan states like the Kingdom of Sennar and Fulani Empire employed Medieval tactics and weapons well after they had been supplanted in Europe. In the Medieval period, feudalism was firmly implanted, and there existed many landlords in Europe. Landlords often owned castles to protect their territory. The Islamic Arab Empire began rapidly expanding throughout the Middle East, North Africa, and Central Asia, initially led by Rashidun Caliphate, and later under the Umayyads. While their attempts to invade Europe by way of the Balkans were defeated by Byzantium and Bulgaria, the Arabs expanded to the Iberian Peninsula in the west and the Indus Valley in the east. The Abassids then took over the Arab Empire, though the Umayyads remained in control of Islamic Spain. At the Battle of Tours, the Franks under Charles Martel stopped short