The second battle of Clusium (82 BC) saw Pompey defeat the remnants of the army of the consul Carbo, after they had been abandoned by their commander (Sulla's Second Civil War).
At the start of the campaign of 82 BC Pompey had served under Metellus Pius, one of Sulla's most senior allies, in a campaign in Cisalpine Gaul. The consul Gnaeus Papirius Carbo moved north to deal with Metellus, and besieged him somewhere in the north. However his colleague Marius the Younger was defeated at Sacriportus, south of Rome, and besieged in Praeneste. Carbo had to abandon his campaign in the north, and moved south with Pompey harassing his movements. Sulla beat him to Rome, and the two generals faced off around Clusium, about eighty miles to the north of Rome. Sulla and Carbo fought an inconclusive day-long battle (first battle of Clusium), while 40 miles to the east/ south-east of Carbo Pompey, who had continued to follow Carbo south, defeated his lieutenant Carinnas at Spoletium.
The situation was then changed by the threat of a large Samnite army, which was moving to lift the siege of Praeneste. Sulla was forced to dash south to save his troops at Praeneste, leaving Carbo free to move north and try and defeat Metellus Pius in his camp at Faventia. Pompey appears to have been left in the vicinity of Spoletium and Clusium.
Carbo's attack ended as a costly failure. His colleague Norbanus decided to go into exile, and Carbo's morale was now collapsing. After another of his armies was defeated at Placentia, and Cisalpine Gaul changed sides, Carbo deserted his men, and fled to Africa.
There were still 30,000 of Carbo's men at Clusium, where they posed a potential threat to Rome. Sulla was still pinned down at Praeneste, and there were also Marian armies under Carinnas and Marcius at large.
Pompey now attacked the comparatively leaderless forces at Clusium, and won a great victory in which he reported inflicting 20,000 casualties on them. The remaining 10,000 men scattered, although their leaders didn’t give up.
Carinnas, Marcius and Brutus Damasippus made one last attempt to lift the siege of Praeneste, and when this failed took part in the Samnite assault on Rome (battle of the Colline Gate). After this failed the defenders of Praeneste gave up, Marius the Younger committed suicide, and the military phase of the civil war came to an end.