The Julio-Claudian principate commenced with Augustus (r. 27 B.C.–14 A.D.), and included the reigns of Tiberius (r. 14–37 A.D.), Gaius Germanicus, known as Caligula (r. 37–41 A.D.), Claudius (r. 41–54 A.D.), and Nero (r. 54–68 A.D.). During this time, Rome reached the height of its power and wealth; it may be seen as the golden age of Roman literature and arts, but it was also a period of imperial extravagance and notoriety. The Julio-Claudians were Roman nobles with an impressive ancestry, but their fondness for the ideals and lifestyle of the old aristocracy created conflicts of interest and duty. They cherished the memory of the Republic and wished to involve the Senate and other Roman nobles in the government. This proved impossible and eventually led to a decline in the power and effective role of the Senate, the elimination of other aristocrats through treason and conspiracy trials, and the extension of imperial control through equestrian officers and imperial freedmen. The emperors’ power rested ultimately on the army, of which they were commanders-in-chief, and they had to earn (as in the case of Claudius) its respect and loyalty. The army not only ensured their control in Rome but also helped maintain peace and prosperity in the provinces.
Tiberius followed the instructions left by Augustus upon his death not to undertake any expansive foreign wars. Relying more on diplomacy than military force, the empire reached an unprecedented peak of peace and prosperity. He maintained a strict economy and spent little on grandiose building projects. The most impressive sculpture begun during his reign and completed under Claudius was the Ara Pietatis, a monumental altar with classical representations that recall those on the Ara Pacis Augustae (late first century B.C.). Tiberius bequeathed a great surplus to his successor, Caligula, whose enormously extravagant games and spectacles eventually emptied the imperial treasury. In matters of government, Caligula favored a monarchy of Hellenistic type and accepted elaborate honors in Rome and in the provinces. The dissemination of imperial portraiture in the provinces, in sculpture, gems, and coins, was the chief means of political propaganda in the Roman empire, and all of the Julio-Claudians subscribed to the basic imperial image established by Augustus. Even Caligula, who was obsessed with his own appearance, adhered to this formula. His reign of extravagance, oppression, and treason trials ended in his assassination in 41 A.D.
Rome prospered during the succeeding reign of Claudius (Caligula’s uncle), who achieved administrative efficiency by centralizing the government, taking control of the treasury, and expanding the civil service. He engaged in a vast program of public works, including new aqueducts, canals, and the development of Ostia as the port of Rome. To the Roman empire, he added Britain (43 A.D.) and the provinces of Mauritania, Thrace, Lycia, and Pamphylia. Imperial expansion brought about colonization, urbanization, and the extension of Roman citizenship in the provinces, a process begun by Julius Caesar, continued by Augustus, slowed by Tiberius, and resumed on a large scale by Claudius.
Under the next emperor, Nero, the frontiers of the empire were successfully defended and even extended. Experienced generals, such as Corbulo and Vespasian, led triumphant campaigns in Armenia, Germany, and Britain. Nero himself was more of a dilettante, and a connoisseur and patron of the arts; his coins and imperial inscriptions are among the finest ever produced in Rome. After a great fire destroyed half of Rome in 64 A.D., he spent huge sums on rebuilding the city and a vast new imperial palace, the so-called Domus Aurea, or Golden House, whose architectural forms were as innovative as they were extravagant. Nero antagonized the upper class, confiscating large private estates in Italy and putting many leading figures to death. His tendency toward Oriental despotism, as well as his failure to keep the loyalty of the Roman legions, led to civil strife and opposition to his reign.