A feeling resembling loyalty had grown up at Rome toward the family of Augustus, and no one ventured to dispute the claim of Tiberius to the throne. Livia, however, who had attended the death-bed of the emperor, concealed his death until her son arrived, and then proclaimed, at the same moment, the death of Augustus and the accession of his successor. The first event of the new reign was the assassination of Agrippa Postumus, grandson of Augustus, and, according to the modern rule of descent, the proper heir to the throne. The guilt of this act was shared between Tiberius and his mother, who were also accused of having hastened the death of Augustus.

Tiberius summoned the Senate to assemble, announced the death of the emperor, and pretended a wish to be relieved from the cares of empire; the Senate, however, refused to accept his feigned resignation, and he yielded to their wishes. This body now became the chief source of legislation. Tiberius took away from the people the power of making laws and of electing magistrates. The senatus consulta, or decrees of the Senate, were made the source of law, without any authority from the Comitia. The Senate selected the Consuls from four candidates presented to them by the emperor, and thus the last trace of the popular power passed away.

Meanwhile two mutinies occurred among the soldiers, which seemed at first to threaten a change in the government. The legions of Pannonia, complaining of long service and indifferent pay, rose against their commander Blæsus, but were induced to return to their duty by Drusus, the son of Tiberius. A more important insurrection broke out among the legions of the Rhine, who sought to prevail upon Germanicus, the son of Drusus, to accept the imperial crown. Germanicus, however, who was adorned with many noble qualities, refused to yield either to their entreaties or their threats. Agrippina, his wife, with the infant Caius, joined Germanicus in imploring the soldiers not to forget their duty; and they at length relented, and even gave up their leaders.

Germanicus had now deserved the hatred of the jealous and treacherous Tiberius. He was beloved by the people and the army, was frank, generous, and brave; he had married Agrippina, the daughter of Julia and Agrippa, and was the adopted son of the emperor himself. His mind had been highly cultivated, and he excelled in all elegant exercises. He seems, in fact, to have been one of the noblest of the Romans.

In A.D. 14 he led an army across the Rhine, but the next year planned a more important expedition, in which he defeated the Germans under Arminius, and buried the remains of the army of the unfortunate Varus under an earthen mound. His third campaign was still more successful. In A.D. 16 he gained an important battle in the valley of the Weser, and recovered the last of the eagles lost by Varus.

Tiberius, jealous of his fame, now recalled him, and resolved that the limits of the empire should not be enlarged. In A.D. 17 Germanicus triumphed, surrounded in his chariot by his five sons. The same year he was sent to the East to settle the affairs of the Eastern provinces. Meanwhile a war broke out in Germany between Arminius and Marboduus. Drusus was sent thither to contrive the destruction of both leaders, which he seems to have effected, since Marboduus was driven to seek protection from the Romans, while the brave Arminius was soon after slain by the hands of his fellow-Germans.

Germanicus, in A.D. 18, visited Athens, sailed up the Nile the same year, and then, having returned to Syria, died of poison administered to him by Cn. Piso, a friend of the Empress Livia. His death excited great grief at Rome, where he was buried with solemnity in A.D. 20. Piso, meanwhile, being tried before the Senate, and finding himself about to be condemned, sought a voluntary death.

Tiberius was cold and unpopular in his manners, awkward and even timid in his carriage, but a master of dissimulation. The only person of whom he stood in awe was his mother Livia; but he lived in constant fear of insurrection. The Lex Majestas, which he enlarged and enforced with unusual severity, was now the source of great evil to his country. This law defined treason against the emperor. Tiberius made it include words as well as acts, and thus he who spoke lightly of the emperor's person or authority might be punished with death.

From this law grew up the Delatores, or informers, persons who made it their chief occupation to denounce those who were obnoxious to the emperor. The informers soon grew numerous: some of them were persons of high rank, who sought to display their eloquence, and to win the favor of the emperor, by denouncing his opponents in envenomed rhetoric, while others were common spies. No man's life was safe at Rome from this moment, and the purest and wisest citizens were exposed to the attacks of an infinite number of delators. Tiberius encouraged the informers. Ælius Saturninus was flung from the Tarpeian Rock for a libel upon the emperor. Silanus was banished for "disparaging the majesty of Tiberius."

Tiberius, who professed to imitate the policy of Augustus in every particular, seems to have governed with firmness and ability. He improved the condition of the provinces, restrained the avarice of the provincial governors, maintained good order in the capital, and strove to check the growth of luxury; but the morals of the capital were now hopelessly depraved, and the vice and corruption of the whole world flowed into the streets of Rome.