Pompey
Pompey during Sulla's civil war

In the year prior to Sulla's return Pompey had raised and equipped a full legion from amongst his father's old clients and veterans in Picenum. In the spring of 83 Sulla landed in Brundusium. As he marched north-west towards Campania, Pompey led his own legion south to join him. The government in Rome sent out three separate armies in an attempt to prevent the union between Pompey's and Sulla's army. Pompey attacked one of these armies and routed it. The three enemy commanders, unable to agree on a course of action, withdrew. Soon after Pompey arrived at Sulla's camp. He was greeted by Sulla with the official title of Imperator (General).

At some point in 83 BC, it is not clear when but definitely before the onset of winter, Sulla sent Pompey back to Picenum to raise more troops. When fighting broke out once more in 82 Sulla advanced towards Rome, while Metellus (one of his lieutenants), supported by Pompey, campaigned against the consul Gaius Papirius Carbo in Cisalpine Gaul. During this campaign Pompey acted as Metellus's cavalry commander.

Metellus and Pompey defeated Carbo's lieutenant, the praetor Gaius Carrinas, in a six-hour battle at the river Aesis, only to be blockaded by Carbo himself. When word of Sulla's victory at the Battle of Sacriportus reached them, Carbo retreated to his base at Ariminium, severely harassed by Pompey's cavalry. Some time later Metellus defeated Gaius Marcius Censorinus, another of Carbo's lieutenants, Pompey's cavalry caught Censorinus's fleeing troops outside their base at Sena Gallica, defeating them and plundering the town. While Metellus remained in the north-west, Pompey seems to have transferred to Sulla's command in the south.

Pompey advanced south-west along the Via Flaminia towards Spoletium, where he joined Marcus Licinius Crassus, together they defeated Carrinas once again. Pompey laid siege to Carrinas in Spoletium but the latter managed to escape. Pompey resumed his march to join Sulla's command. Not long afterwards Pompey successfully ambushed another large force under Censorinus, which was trying to get through to Praeneste where Carbo's consular colleague, Marius the Younger (who was the figurehead of the struggle against Sulla), was blockaded. It was the failure of these attempts to get through the Sullan blockade in Umbria and Etruria, added to Metellus's success in winning control of the north, which broke the back of the government's resistance.

At the end of the campaigning season of 82, the government forces made one final effort to march to the relief of Praeneste. They mustered 10,000 legionaries and marched to join forces with the Samnites and the Lucanians, fierce enemies of Sulla, who had campaigned against them in the Social War. Pursued by Pompey they united their forces and made for Praeneste. Unable to break through Sulla's blockade, they marched for undefended Rome, only to be caught just in time and defeated by Sulla at the Battle of the Colline Gate. Pompey, who was pursuing the government forces, arrived just after the battle.

By the end of 82 BC, Sulla had expelled his opponents from Italy, and engineered his nomination as Dictator by the Senate. Either through admiration of his abilities, or concern at his ambition, Sulla sought to consolidate his alliance with Pompey by persuading him to divorce Antistia, and marry his stepdaughter Aemilia. Plutarch claims she was already pregnant by her former husband, and died in childbirth soon after.
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