L. Junius Brutus Damasippus (d.82 BC) was a supporter of the Marians during Sulla's Second Civil War, and is most famous for carrying out the murder of four of the younger Marius's enemies.
He may first appear in 83 BC, when Pompey began to raise forces to support Sulla. The consuls sent three armies against him, under Carinnas, Cloelius and Junius Brutus. Pompey turned on Brutus's army, defeated his cavalry, and all three armies retreated. However this may also have been a M. Junius Brutus, another opponent of Sulla active at the time (not to be confused with M. Junius Brutus the elder, father of Brutus the assassin of Caesar, who served as tribune in 83 BC).
Our Brutus first firmly appears in the records in 82 BC, when he was serving as the city praetor of Rome. Marius the Younger, one of the consuls for the year, was defeated by Sulla at Sacriportus, and besieged at Praeneste. He managed to get a message out of the besieged town, ordering Brutus to kill four of his enemies in Rome, and to kill them within the senate.
The first two of his targets, Publius Antistius (a former aedile and father in law of Pompey the Great) and Gaius Papirus Carbo (nephew of Marius's fellow consul and ally Gnaeus Papirus Carbo) were both killed by assassins within the senate house. Licius Domitius Ahenobarbus, one of the consuls for 94 BC, got a little further and was killed by the senate door. Finally Quintus Mucius Scaevola, pontifex maximus and an expert of Roman law, was killed in the temple of the Vestal Virgins. Their bodies were then thrown into the Tiber.
Soon after this, Sulla occupied Rome. Brutus fled from the city along with most of the Marian leaders before his arrival.
Brutus reappears (as Damasippus) towards the end of the civil war. After suffered a defeat at Faventia, Carbo made one last attempt to lift the siege of Praeneste, sending Brutus with two legions to try and force his way past Sulla. This was something of a forlorn hope, and the attempt failed. Soon afterwards Carbo fled into exile in Africa.
Carbo left behind an army of 30,000 men, but this was shattered by Pompey the Younger (Second battle of Clusium). In the aftermath of this defeat the last remaining Marian leaders - Brutus Damasippus, Carinnas and Marcius - gathered what forces they could, and made a four unsuccessful attempt to lift the siege of Praeneste.
The Samnites, who had also been attempting to lift the siege, now decided to attack Rome. They were defeated by Sulla in a desperate battle outside the Colline Gate. Brutus was captured either during or soon after the battle, beheaded, and his head sent to Praeneste, along with that of the other captured Marian leaders.
His death was said to have been welcomed at the time, but also to have been the first sign of the proscriptions to follow, in which many who had celebrated the death of Damasippus were then executed.
It is possible that Damasippus had been adopted by one of the Licinia, a family that included two men named Licinius Damasippus during this period, although the name could also mean 'tame of horses'.