Tiberius succeeded Augustus as Emperor of Rome in September 14 CE. Caligula succeeded Tiberius in 37 CE. Claudius did not become Emperor until 41 CE, after the short-lived and incredibly tumultuous reign of Caligula.

Nerva was relatively mild, moderate Emperor who was appointed to the position after a lifetime of service by the Senate. While Domitian was assassinated by his guards, Nerva was not involved in the plot. Nerva ruled for just under two years before he died of natural causes.

Marcus Aurelius ascended to the position of emperor in 161 CE and ruled for just shy of 20 years. He was the preceding emperor (Antonius Pius)'s son-in-law, adopted son, and named heir. Antonius Pius died of natural causes.

Caligula was succeeded by Claudius, after Caligula was assassinated in 41 CE. While Roman Senators were involved in the plot, they never technically ousted him; Caligula was the ruling emperor at the time of his death, thus the only correct answer is that his rule was ended by his assassination.

The Year of the Four Emperors occurred in 69 CE. Following the flight and suicide of Emperor Nero, Galba was recognized as emperor.

Shortly after, Galba had quickly lost popularity among the Praetorian Guard and other Roman legions by destroying or charging enormous taxes to towns that did not accept him as ruler immediately. He was murdered by the Praetorian Guard and replaced by Otho.

Otho ruled for a short time before another legion, this time led by Vitellius, decided to take power for himself. Vitellius' legions defeated Otho's forces and Otho committed suicide shortly after, leaving Vitellius as emperor.

Similar to Otho, Vitellius ruled for a short time before showing his violent and tyrannical nature. He soon suffered a military defeat by the armies of Vespasian, and was killed by Vespasian's men. This allowed Vespasian to become the fourth emperor in the span of just a single year.

Augustus Caesar (formerly called Octavian) was the first Emperor of Rome. He is popularly remembered for saying, “I found Rome a city of bricks and left it a city of Marble.” This quote is meant to summarize the great changes in the power of Rome that began with the reign of Augustus Caesar. It is also meant to demonstrate the great public works projects undertaken on Augustus’ orders to beautify and urbanize the city of Rome.

The Pax Romana refers to a period of time when the Roman Empire enjoyed relative peace and prosperity. The Pax Romana is said to begin with the reign of Augustus Caesar (the first Emperor) in 27 BCE. It lasted until 180 CE. During this time period, the various nationalities living within the Roman Empire experienced peace with one another (with the exception of a few notable uprisings). Furthermore, Rome undertook relatively few military campaigns to expand foreign territory.

Caligula was the third Emperor of Rome and ruled for four years after the death of Tiberius. Caligula’s reign was apparently marked by peace and prosperity for the first year or so, before Caligula suddenly descended into madness and brutality. It is unclear, from a modern historical perspective, if Caligula really did go insane or if he was merely the victim of the slanderous propaganda of later political regimes.

Tiberius was the second Emperor, following on from Augustus Caesar. Tiberius is one of the most accomplished conquerors in the history of the Roman Empire. Tiberius reigned from 14 CE until 37 CE.

For five-hundred years, from the late sixth century BCE until 27 BCE, Rome was a republic and power was shared by various republican institutions. After the various civil wars of the first century BCE, however, power was consolidated in the hands of Augustus Caesar, first emperor of Rome.