2. M.Petreius, is first mentioned in B. C. 62, when he served as legatus to the proconsul C. Antonius, in his campaign against Catiline. Both Cicero and Sallust speak of Petreius as a man of great military experience, and one who possessed considerable influence with the troops. He had previously served in the army more than thirty years, either as tribune, praefectus, legatus, or praetor; but we know nothing of his former history, nor in what year he was praetor. In consequence of the illness of Antonius, according to one statement, or his dislike to fight against his former friend, as others rltate, the supreme command of the army devolved upon Petreius on the day of the battle, in which Catiline perished. (Sal. Cat. 59, 60; D. C. 37.39, 40; Cic. pro Sest. 5.) The name of Petreius next occurs in B. C. 59, in which year he offered to go to prison with Cato, when (Caesar, the consul, threatened the latter with this punishment. (D. C. 38.3.) In B. C. 55 Petreius was sent into Spain along with L. Afranius as legatus of Pompey, to whom the provinces of the two Spains had been granted. On the breaking out of the civil war in B. C. 49, Afranius and Petreius were in Nearer Spain at the heaof so powerful an army, that Caesar, after obtaining possession of Italy, hastened to Spain to reduce those provinces. Afranius and Petreius, on the approach of Caesar, united their forces, and took up a strong position near the town of Ilerda (Lerida in Catalonia), on the right bank of the Sicoris (Segre). At first they were very successful, and Caesar was placed in great difficulties; but these he quickly surmounted, and soon reduced the enemy to such straits, that Afranius and Petreius were obliged to surrender. They were dismissed uninjured by Caesar, part of their troops disbanded, and the remainder incorporated in the conqueror's army. Petreius joined Pompey in Greece, and after the loss of the battle of Pharsalia in B. C. 48, he first fled to Patrae in Achaia, and subsequently passed over to Africa. He took an active part in the campaign in Africa in B. C. 46. At the battle of Ruspina, fought at the beginning of January in this year, he was severely wounded; and he was also present at the battle of Thapsus in the month of April, by which Caesar completely destroyed all the hopes of the Pompeian party in Africa. After the loss of the battle Petreius fled with Juba to Zama, and as the inhabitants of that town would not admit them within its walls, they retired to a country house of Juba's, where despairing of safety they fell by each other's hands. The exact manner of their death is somewhat differently related by different writers. According to some accounts Juba despatched Petreius first and then killed himself, while the contrary is stated by others. (Cic. Att. 8.2; Caes. Civ. 1.38, 63_86; Hirt. B. Afr. 18, 19, 91, 94; D. C. 41.20, 42.13, 43.2, 8; Appian, App. BC 2.42, 43, 95, 100 ; Lucan, 4.4, &c.; Vell. 2.48, 50; Suet. Jul. 34, 75; Liv. Epit. 110, 114.)