After the death of Emperor Marcus Aurelius in 180 A.D., his son Commodus became the ruler of the Roman Empire. Commodus loved blood sports. Civil war broke out immediately after his death, as numerous military officers fought for control of the empire. After much strife, Septimus Severus emerged as the new Roman emperor. Severus ruled as a military dictator. Following his death, Rome was ruled the next 50 years by 26 emperors. Only one of these died of natural causes. During this time period Rome was always on the verge of collapse. This created an environment where civil war was constant. At the same time, the Roman Empire was being attacked by Germanic tribes on the northern border and the Persian Empire on the eastern border.
Then, by 284 A.D., the military temporarily restored the empire. However, the government was broken, and inflation was running wild, and the depleted government kept raising taxes. Making things even worse, trade declined because they weren't producing anything to export. Almost everything had to be imported from the east. Things got so bad that nothing was being grown, People simply abandoned their farms. Productivity died as well, because of the lack of new agrarian technology. The entire middle class disappeared. During this incredible period of turmoil emerged the most efficient Roman emperor since Augustus. His named was Diocletian. Diocletian became ruler after earning the respect of his men on the battlefield, but before he could return the country to stability and institute meaningful reforms he would again have to defeat the enemy four more times.
Diocletian believed that the empire was too large to be ruled by one person. He decided on a system of four rulers. This system is called a tetrarchy. Diocletian would have two co-emperors, and they would each have a secondary emperor who was called a Caesar. Diocletian and his Caesar who was named Galerius, controlled the eastern half of the empire, and Diocletian's close friend Maximian, and his Caesar named Constantius, ruled the western half of the empire. Next, Diocletian increased the number of provinces from 50 to 100, making them more manageable. Each was ruled by a governor. Then he divided the provinces into 13 dioceses, and he divided the dioceses into four parts, which were called a prefectures. When he organized the government in this way it lessened the chances for eternal revolts and civil wars. Next, in order to stop inflation, he froze the prices for all goods, transportation, and wages. Diocletian created a totalitarian state, and the senate no longer existed. However, he stopped the economic decline.
After Diocletian's death, civil war broke out as five men fought for control of the empire. Constantine emerged the leader, and he became the sole ruler in 324 A.D. He moved the capital of the eastern half of the empire to the Greek city of Byzantium, and changed the name to Constantinople. At the same time the patriarch in Rome became the pope of the Roman Catholic Church, while the patriarch in Constantinople became the leader of the Orthodox Church. Now the empire was permanently split, but Constantine maintained control over the ruler in the west. Then, after his death, Emperor Theodosius divided the empire between his two sons. It would never be united again.