After the assassination of Domitian in 96, and amid the predictable turmoil of the regime change, Tacitus used his new-found freedom to publish this, his first historical work. During the reign of Domitian, Agricola, a faithful imperial general, had been the most important general involved in the conquest of a great part of Britain. The proud tone of the Agricola recalls the style of the laudationes funebres (funeral speeches). A quick resume of the career of Agricola prior to his mission in Britain is followed by a narration of the conquest of the island. There is a geographical and ethnological digression, taken not only from notes and memories of Agricola but also from the De Bello Gallico of Julius Caesar. The content is so varied as to go beyond the limits of a simple biography, but the narration, whatever its form, serves to exalt the subject of the biography.
Tacitus exalts the character of his father-in-law, by showing how — as governor of Roman Britain and commander of the army — he attends to matters of state with fidelity, honesty, and competence, even under the government of the hated Emperor Domitian. Critiques of Domitian and of his regime of spying and repression come to the fore at the work's conclusion. Agricola remained uncorrupted; in disgrace under Domitian, he died without seeking the glory of an ostentatious martyrdom. Tacitus condemns the suicide of the Stoics as of no benefit to the state. Tacitus makes no clear statement as to whether the death of Agricola was from natural causes or ordered by Domitian, although he does say that rumors were voiced in Rome that Agricola was poisoned on the Emperor's orders.
For Tacitus, Agricola served as an example of how, even under a despotism, it was possible to behave correctly, avoiding the opposite extremes of servility and useless opposition. The work can be viewed as an apologia for a large part of the governing class: people who, not desiring martyrdom, had collaborated with the Flavian family and had made a valid contribution to lawmaking, to provincial government, to the enlargement of the limits of the empire and to the defence of its borders. On the other hand, the work may well have been a plea to the recently re-instated Stoics not to harass and oppose the new regime in a time of great instability.
The work has a strong anti-despotic tone. Tacitus sets the despotism of Domitian against the merits of Agricola: an incorruptible officer and a great commander, who fitted the model of the mos maiorum ("the custom of the forefathers", the presumed superior morality of an earlier time). The writer implicitly says that, as the Empire should be accepted as a necessary evil, one has to keep one's dignity without mixing up one's own responsibility with the responsibility of an arbitrary despot like Domitian. One can be an honest and scrupulous officer, doing his job with serenity and in collaboration with the regime, keeping his job and keeping the interest of the state, waiting for a better age, when a writer would be able to write in freedom.
The Agricola mixes various literary genres. It is an elegy evolved into a biography, a laudatio funebris mixed with historical and ethnographical material. For this reason, the book contains portions written in different styles. The exordium, the speeches, and the final peroration show strong influence from Cicero, probably derived from Tacitus's own training in rhetoric. In the narrative and ethnographical portions, two models of the historical style can be seen: that of Sallust (with incongruities, archaism, parataxis and sobriety) and that of Livy (with oratorical style: wide, fluid, hypotactic and dramatic).