During the five centuries of its existence, the Roman Empire (27 B.C.–A.D. 476) was ruled by noteworthy as well as infamous leaders. For example, after his uncle Julius Caesar was murdered, Octavian, (63 B.C.–A.D. 14; also called Augustus) became Rome's first emperor. He ruled during the Pax Romana (a period of peace). This peace allowed the arts, literature, education, and commerce to flourish.
The second emperor of Rome was Augustus's adopted son Tiberius (42 B.C.–A.D. 37). Tiberius was a good administrator, but his economic measures made him unpopular with senators, who plotted his downfall. Tiberius's nephew Caligula (A.D. 12–41; born Gaius Caesar) ascended the throne upon Tiberius's death. After a short period of rule, Caligula became ill. Thereafter he demonstrated the erratic (unusual) behavior for which he is infamous and because of which many scholars believe he was insane. After Caligula was murdered in A.D. 41, Claudius, another nephew of Tiberius, took the throne. Claudius (10 B.C.–A.D. 54) expanded the borders of the Roman Empire to include half of Britain. Scholars believe that, like Caligula, Claudius was murdered. Claudius's demise made way for Nero, Claudius's adopted son, to ascend the throne. Nero (A.D. 37–68) ruled wisely for a time, but after A.D. 59 he became ruthless. He persecuted Christians, ordered the murder of many Romans, and spent tax money to support his lavish lifestyle. When the Roman Senate turned against him in the year 68, Nero committed suicide.
While the early Roman Empire suffered under despotic (harsh) rulers, later leaders were more moderate. Trajan (A.D.53?–117) ruled the empire for nineteen years, expanding its territory through military campaigns and constructing roads, bridges, and buildings. When Marcus Aurelius (121–180) became emperor in 161, he brought a wealth of experience in ruling. Under his leadership the Romans repelled Germanic and Syrian invaders. Also a Stoic philosopher (advocate of the view that humans should not be ruled by emotion), Marcus Aurelius tried to lessen the effects of famine and plague on the empire, lowered taxes, tried to improve the treatment of slaves, and founded schools, orphanages, and hospitals. Despite making these positive contributions, Marcus Aurelius harshly persecuted Christians (followers of the religion founded by Jesus of Nazareth, also called the Christ).
Army commander Diocletian (A.D. 245?–313?) became emperor in 284. He divided the empire into four regions, each under the command of its own ruler, who reported to the emperor. Diocletian ordered Christians to be persecuted, a measure that Constantine I countermanded (cancelled) when he became emperor after Diocletian's retirement in 306. Constantine I (also known as Constantine the Great) reunited the four regions as a single Roman Empire. He was also the first Roman emperor to convert to Christianity. Theodisius I (347–395), who reigned from 379 to 395, was the last emperor to rule a united Roman Empire.
Further Information: Casson, Lionel. "In the Year 1, Augustus Let the Good Times Roll." Smithsonian. August, 1999, p. 82; Halsall, Paul, ed. Internet Ancient History Sourcebook. [Online] Available http://www.fordham.edu/halsall/ancient/asbook.html, October 26, 2000; Moulton, Carroll. Ancient Greece and Rome: An Encyclopedia for Students. New York: Simon and Schuster, 1998; Nardo, Don. Age of Augustus. San Diego, Lucent, 1996; Nardo, Don. Rulers of Ancient Rome. San Diego: Lucent, 1999.