In the aftermath of Nero's death, a brief civil war broke out. Four generals competed for the emperorship, supported by their armies. In the end, a general named Vespasian (r. 69 – 79 CE) seized power and founded a fairly short-lived dynasty consisting of himself and his two sons, known to history as the Flavians. The importance of Vespasian’s takeover was that it reinforced the idea that real power in Rome was no longer that of the old power-broking families, but instead the armies; Vespasian had no legal claim to the throne, but his emperorship was ratified by the senate nevertheless. The emperor's major concern had to be maintaining the loyalty of the armies above all else, because they could and would openly fight to put their man on the throne in a time of crisis - this occurred numerous times in the centuries to come.
Vespasian was one of the great emperors of the early empire. He pulled state finances back from the terrible state they had been left in by Nero and restored the relationship between the emperor and the Roman elite; it certainly did not hurt his reputation that he was a successful general, one of the traditional sources of status among Roman leaders. He was also renowned for his openness and his grounded outlook. Reputably, he did not keep a guard and let people speak to him directly in public audiences. In an act of classic Romanitas, he started work on the famous Colosseum (known at the time as the Flavian Amphitheater) in Rome in order to provide a grand setting for public games and performances. All of this happened in just a decade; he died of natural causes in 79 CE.
Vespasian's older son Titus (r. 79 – 81 CE) had been groomed to follow his father and began as a promising and competent emperor. Unfortunately, almost as soon as he took the throne a volcano in southern Italy, Mt. Vesuvius, erupted, followed shortly by another huge fire as well as an epidemic in Rome. Titus struggled to aid victims of all three disasters, but was then struck by fever and died in 81 CE.
Vespasian's second son, Domitian (r. 81 – 96 CE), who was not "supposed" to take the throne, proved to be a terrible ruler. He created an atmosphere of terror in elite Roman circles in an effort to watch out for potential rebels, murdering senators and elites he suspected. He adopted a Caligula-like concern for glorifying himself (like Caligula, he insisted that he be addressed as “dominus et deus”) and liked to appear before the senate in the armor of a Roman commander returning from victory. He was moralistic about both sex and the divinity of the emperors, instituting the policy that all oaths had to be sword to the godhood of the emperor. About the only positive undertaking in his rule was major building projects, both for palaces for himself and public works (including roads and fortifications), and it is also worth noting that the empire remained under a stable administration during his reign. That noted, Domitian became increasingly paranoid and violent between 89 and 96 CE, until he was finally killed by assassins in the palace.