The battle of the Colline Gate (1 November 82 BC) saw a largely Samnite army come dangerously close to capturing Rome, taking advantage of the distraction caused by Sulla's Second Civil War.
Early in the campaign of 82 BC Marius the Younger, one of the consuls for the year, had suffered a heavy defeat at the battle of Sacriportus, and was besieged in Praeneste, only 40 miles to the south of Rome. Sulla left Q. Lucretius Ofella to conduct the siege and moved to occupy Rome, while the second consul for the year, Gnaeus Papirius Carbo, abandoned a campaign in Cisalpine Gaul and moved back to Clusium, eighty miles to the north of Rome. A series of battles around Clusium were inconclusive (first battle of Clusium, battle of Spoletium), but Carbo's attempts to lift the siege of Praeneste also failed.
The situation changed when a large army of Italians, who had supported the Marians since Sulla's First Civil War, was discovered to be heading for Praeneste. Appian reports that this army was 70,000 strong, and was led by the Samnite Pontius Telesinus, the Lucanian Marcus Lamponius (a survivor of the Social War) and the otherwise unknown Gutta the Capuan. Sulla was forced to dash south to prevent this army from reaching Praeneste. Appian states that he blocked a pass on the only approach to Praeneste, a problematic description as there is no obvious candidate for this pass. He was then able to stop the Samnites. At the same time Marius attempted to break out of Praeneste, but Ofella was able to stop him and the siege resumed.
A standoff now developed around Praeneste, but in the north the Marian cause was beginning to collapse. Carbo attempted a surprise attack on Metellus Pius's camp at Faventia, in the south of Cisalpine Gaul, but suffered a heavy defeat. His colleague Norbanus decided that the war was lost and fled into exile. Carbo's last attempt to raise the siege of Praeneste failed, Cisalpine Gaul abandoned his cause, and his army in the area was defeated at Placentia. Carbo now followed Norbanus into exile, fleeing to Africa. His deserted army was defeated by Pompey (second battle of Clusium), and broke up.
Although the Marian cause was fading, its remaining leaders didn’t give up. Carinnas, Marcius and Brutus Damasippus gathered together what troops they could, and made one last attempt to lift the siege of Praeneste, alongside the Samnites.
When this final attempt failed, the Marian leaders decided to risk everything on an attack on Rome. The city was undefended, and dangerously vulnerable to attack.
The Samnites and their allies clearly caught Sulla by surprise. By the end of the first day after leaving Praeneste, they had reached the Alban Hills, and camped only 11 miles from Rome.
Sulla sent his cavalry to try and delay the enemy advance, and then led the fest of his army back towards Rome.
On the second day of their march (the Kalends or 1st of November) the Samnites reached Rome, and took up a position around the walls. Soon after dawn a force of young nobles came out of the city to attack the Samnites, but they were outnumbered and inexperienced, and were overwhelmed. Amongst the defeated nobles was a young Appius Claudius, although it isn't clear which member of that important family this was.
Rome was now in great danger, the worst since Hannibal had camped outside the city. Velleius Paterculus provides us with the words of Telesinus - 'The last day is at hand for the Romans. These wolves that have made such ravages on Italian liberty will never vanish until we have cut down and destroyed the forest that harbours them'.
The first of Sulla's men to arrive was a force of 700 cavalry under Balbus. They paused for a few moments to let their horses recover, and then plunged into the battle.
Sulla arrived at the northern end of the city at about noon, and encamped by the Colline Gate, near the temple of Venus, which was then outside the walls. He ordered his men to eat, and then form into order of battle, ready to attack. His lieutenants, Dolabella and Torquatus, urged him to give his men to time to recover from the march, as their opponents were Samnites and Lucanians and thus more dangerous than Carbo or Marius.
Sulla refused to accept their advice, and attacked at around four in the afternoon (Orosius says the ninth hour of the day, between about 2 and 3pm at that time of year.
Sulla's left wing was hard pressed. Sulla attempted to restore the situation in person, but his white horse made him an obvious target, and he was only saved from injury by the quick thinking of his groom, who whipped Sulla's horse, making it rush forward. Despite all of his efforts, Sulla's left was defeated. Some of his troops fled into the city.The walls were defended by some of the old soldiers who lived in Rome, and when they saw some of the Samnites coming through the gates along with the refugees, they dropped the portcullis, killing a number of senates and soldiers. A number of people who had come out of the city to watch the battle were also killed. Some of Sulla's men fled to Praeneste, where they tried to convince Ofella to lift the siege as the battle for Rome had been lost. Ofella took no notice, and persisted with the siege. Finally, Sulla and some of his men managed to get back to his camp near the Colline Gate.
Sulla's right wing, which was commanded by Crassus, was victorious. Sulla didn't discover this until late in the night, when a message arrived from Crassus asking for food for his men. He had defeated the Samnite left and pursued them as far as Antemnae, two miles north of the city.
The battle continued into the night. Telesinus and Albinus were killed and their camp was captured. Velleius Paterculus reports that Telesinus was found half dead on the day after the battle, but with the 'expression of a conqueror upon his face rather than that of a dying man'.
Lamponius the Lucania, Marcius and Carinnas escaped from the battle, but Marcius and Carinnas were captured and executed on the following day.
On the day after the battle Sulla joined Crassus at Antemnae. Some of the inhabitants of the town sent messengers to Sulla to sue for mercy. He agreed to spare them if they would first attack their fellow defenders. This triggered a battle within Antemnae, after which Sulla took 6,000 prisoners from both sides.
In the aftermath of the battle Sulla massacred a number of the prisoners, making sure that the killing began at the same time as he was addressing the Senate. Plutarch places the massacre in the circus, while the Senate as meeting in the temple of Bellona. Livy puts the killings in the Villa Publica, on the Campus Martius to the west of the city, near the Circus Flaminius. Amongst these prisoners were the 3,000 men who had surrendered on terms,
When the Senators asked what was going on, Sulla replied that it was 'nothing more than the screaming of a few criminals paying the just penalty for their crimes'
Appian reports casualty figures of 50,000 on each side, and that Sulla had 8,000 Samnite prisoners killed with darts.
Marcius, Carinas and Telesinus were beheaded and their heads were sent to Praeneste, where they were displayed outside the walls. This convinced the defenders to surrender. Marius the Younger attempted to escape, but his route was blocked and he committed suicide.
This ended the military phase of the civil war, but it was now followed by Sulla's prescriptions. Official lists of the 'guilty' were published in Rome, and anyone could then kill them and claim reward. Appian says that 40 senators and 1,600 knights were proscribed. Plutarch in his life of Sulla has the proscriptions begin with a list of 80, followed by two lists of 220, for a total of 520 proscriptions in three days. It was also illegal to help anyone who had been proscribed, and again the punishment was death. The same happened across Italy, where any sign of support for the defeated faction could lead to a death sentence, as could the possession of riches.