*The conspiracy of Piso, 65 A. D.* About 62 A. D. there began a long series of treason trials in Rome occasioned partly by the desire to confiscate the property of the accused and partly by the suspicion which is the inevitable concomitant of tyranny. The resulting insecurity of the senatorial order naturally produced a real attempt to overthrow the princeps. A wide-reaching conspiracy, in which one of the praetorian prefects was involved and which was headed by the senator Gaius Calpurnius Piso, was discovered in 65 A. D. Among those who were executed for complicity therein were the poet Lucan and his uncle Seneca. Other notable victims of Nero’s vengeance were Thrasea Paetus and Borea Sonarus, the Stoic senators, whose guilt was their silent but unmistakable disapproval of his tyrannical acts. No man of prominence was safe; even the famous general Corbulo was forced to commit suicide in 67 A. D. *The rebellion of Vindex, 68 A. D.* Upon Nero’s return from Greece, a more serious movement began in Gaul where Caius Julius Vindex, the legate of the province of Lugdunensis, raised the standard of revolt and was supported by the provincials who were suffering under the pressure of taxation. Vindex was joined by Sulpicius Galba, governor of Hither Spain, and other legates. The commander of Upper Germany, Verginius Rufus, who remained true to Nero, defeated Vindex, but, the revolt spread to the troops of Verginius himself and these hailed their commander as imperator. He, however, refused the honor and gave the Senate the opportunity to name the princeps. Nero’s fate was sealed by his own cowardice and the treachery of the prefect Sabinus, who bought the support of the praetorian guards for Galba. The Senate followed their lead, and Nero, who had fled from Rome, had himself killed by a faithful freedman. With him ends the Julio-Claudian dynasty. V. THE FIRST WAR OF THE LEGIONS OR THE YEAR OF THE FOUR EMPERORS, 68–69 A. D. *The power of the army.* The year 68–69 witnessed the accession of four emperors, each the nominee of the soldiery. And, while up to this time the praetorians had exercised the right of acclamation in the name of the army as a whole, now the legions stationed on the various frontiers asserted for themselves the same privilege. As Tacitus expresses it, the fatal secret of the empire was discovered, namely, that the princeps could be nominated elsewhere than in Rome. Although the principate may be said to have been founded by the universal consent of the Roman world, nevertheless, from its inception the power of the princeps had rested directly upon his military command, and the civil war of 68–69 showed how completely the professional army was master of the situation.