Short answers, pulled from the story.
Sallust, born around 86 BC as Gaius Sallustius Crispus, was a Roman historian and politician from a plebeian Sabine family. He is the earliest known Latin historian with surviving complete works: Conspiracy of Catiline, the Jugurthine War, and fragments of a larger history called the Historiae.
Sallust was probably born at Amiternum in central Italy in the country of the Sabines, around 86 BC. Some scholars, including Eduard Schwartz, have argued his birthplace was Rome, and the exact birth date has been debated, with suggestions ranging from 87 BC to the 80s BC.
Sallust was a Caesarian partisan during the civil war of 49-45 BC, though his role was not prominent enough to appear in Caesar's own Commentarii de Bello Civili. He served in Illyricum, was probably made quaestor by Caesar in 48 BC, narrowly survived a soldier rebellion in 47 BC, and in 46 BC organised supply operations through the Kerkennah Islands during the African campaign.
After returning from his corrupt governorship of Africa Nova in late 45 or early 44 BC, Sallust faced extortion charges and had no realistic path to further political advancement. He turned to writing history, framing it as an extension of public life to record achievements for future generations.
Sallust's core theme is moral and political decline. He argued that Rome's fall began with the destruction of Carthage in 146 BC, which removed the foreign threat that had kept Roman virtue disciplined, and was worsened by the influx of eastern wealth following Sulla's First Mithridatic War.
Sallust's prose was deliberately archaic, brief, and abrupt, contrasting sharply with Cicero's long harmonious periodic sentences. He used rare and obsolete Latin words, some appearing nowhere else in surviving Latin before him, and scholars have described his approach as anti-Ciceronian.