Sallust's Conspiracy of Catiline uses history as a vehicle for his judgment on the degradations of of Roman morality and politics over time. In that regard, Sallust was one of the first ancient historians to actually offer analysis of events rather than a simple retelling of just the facts. The ancient world admired him for it: Sallust drew praise from the historian Tacitus, and Quintilian compared him favorably with Thucydides.
The Conspiracy of Catiline takes place in the year 63 B.C., with the work looking at the conspiracy of Catiline, who was accused of attempting to overthrow the Roman Republic. Catiline is described as the deliberate foe of law, order and morality. And not incidentally, Catiline was a political opponent of Sallust, who supported Caesar and thus disliked Sulla.
In writing about the conspiracy of Catiline, Sallust's tone, style, and descriptions of aristocratic behavior show him as deeply troubled by the moral decline of Rome. While he inveighs against Catiline's depraved character and vicious actions, he does not fail to state that the man had many noble traits, indeed all that a Roman man needed to succeed. In particular, Sallust shows Catiline as deeply courageous in his final battle.