The Roman Emperors
After the Republic ended, Rome was ruled by a series of emperors, beginning with the Julian Emperors who were all related to Julius Caesar. Tiberius, the adopted son of Augustus, continued Augustus's policies. Caligula (nicknamed "little boots") started as a good emperor but eventually "lost it." Claudius reconquered England and provided welfare programs, while Nero became infamous for his cruelty and forcing people to worship him as a living god.
The period of the "Good Emperors" followed, including Nerva, a wise general; Trajan, considered the greatest emperor who focused on helping others rather than himself; Hadrian, known for his fairness; and Marcus Aurelius, a philosopher who promoted education and citizens' rights. During this time, Rome enjoyed its greatest prosperity.
Eventually, the empire began to decline until Diocletian attempted to revive it by dividing the empire into four regions with four rulers. Later, Constantine fought for control in a civil war. Before the crucial Battle of Milvian Bridge, Constantine reportedly saw a vision of a cross with the message "By this sign, victory." After winning, he issued the Edict of Milan, which allowed religious freedom, and established the Roman Catholic Church.
Critical moment: At the Council of Nicaea, Constantine brought Christian leaders together to establish core beliefs and determine which books would be included in the Bible—a meeting that shaped Christianity for centuries to come.