From Pearce, J. W. E. 1901. The Agricola of Tacitus. London: George Bell and Sons. Pp. xii-xiii.
Tacitus' earliest work is the Dialogus de caussis corruptae eloquentiae, in which he appears as an imitator of Cicero. This suggests the thought that he may have studied rhetoric under Quintilian, who attempted a Ciceronian revival. The work, however, shows some traces of Tacitus' later manner.
His next work, the Agricola, was written about the beginning of Trajan's reign (A.D. 98). It represents what is called the Sallustian period of Tacitus' literary development. Besides the numerous imitations of Sallustian diction, which admitted poetical and colloquial elements, the general arrangement of the Agricola corresponds closely (with the exception of the epilogue, which is Ciceronian in character) to the form of Sallust's monographs, the Catiline and the Jugurtha. (See Index, s.v. Sallust, and Introduction, p. xviii, 'Plan of the Agricola.')
The Germania was published about the same time. It was a patriotic work, written with the purpose of awakening the Romans to the dangers which threatened them from a hardy and unspoilt nation.
The Histories – an account of the reigns of the emperors from Galba to Domitian – were probably published early in Trajan's reign. Of fourteen books, only the first four and part of the fifth remain. They mark a further step in the direction of Tacitus' final style, but do not show the extreme conciseness of the Annals.
(xiii) The Annals in sixteen books, of which seven to ten and part of five are lost, give the history of the Empire from the death of Augustus to the death of Nero, at which point the Histories begin. From the fact of its mentioning Trajan's later conquests, the work cannot have been published long before the end of Trajan's reign. The style is frankly that of the ' Silver Age,' but, as Cruttwell says in his History of Roman Literature, Tacitus 'has glorified it in adopting it.’