As Cinna's death reverberated throughout the Roman world, Sulla realized his opportunity to take full advantage. In 83 BC Sulla prepared his 5 legions and left the 2 originally under Fimbria to maintain peace in Asia Minor. In the spring of that year, Sulla crossed the Adriatic with a large fleet from Patrae, near Corinth, to Brundisium and Tarentum in the heel of Italy. Landing uncontested, he was given ample opportunity to prepare for the coming war.
In Rome, the newly elected Consuls, L. Cornelius Scipio Asiagenus and C. Norbanus levied and prepared armies of their own to stop Sulla and protect the Republican government. Norbanus marched first with the intention of blocking a Sullan advance at Canusium. Seriously defeated Norbanus was forced to retreat to Capua where there was no respite. Sulla followed his defeated adversary and won another victory in a very short time. Meanwhile Asiagenus was also on the march south with an army of his own. Asiagenus or his army, however, seemed to have little motivation to fight. At the town of Teanum Sidicinum, Sulla and Asiagenus met face to face to negotiate and Asiagenus surrendered without a fight. The army sent to stop Sulla wavered in the face of battle against experienced veterans, and certainly along with the prodding of Sulla's operatives, gave up the cause, going over to Sulla's side as a result. Left without an army, Asiagenus had little choice but to cooperate and later writings of Cicero suggest that the two men actually discussed many matters regarding Roman government and the Constitution.
Sulla let Asiagenus leave the camp, firmly believing him to be a supporter. He was possibly expected to deliver terms to the Senate but immediately rescinded any thought of supporting Sulla upon being set free. Sulla later made it publicly known that not only would Asiagenus suffer for opposing him, but that any man who continued to oppose him after this betrayal would suffer bitter consequences. With Sulla's three quick victories, though, the situation began to rapidly turn in his favor. Many of those in a position of power, who had not yet taken a clear side, now chose to support Sulla. The first of these was Q. Caecilius Metellus Pius who governed Africa. The old enemy of Marius, and assuredly of Cinna as well, led an open revolt against the Marian forces in Africa. Additional help came from Picenum and Spain. Two of the three future Triumvirs joined Sulla's cause in his bid to take control. Marcus Licinius Crassus marched with an army from Spain, and would later play a pivotal role at the Colline Gates. The young son of Pompeius Strabo (the butcher of Asculum during the Social War), raised an army of his own from among his father's veterans and threw his lot in with Sulla. At the tender age of 23, and never having held a Senatorial office, Pompey forced himself into the political scene with an army at his back.
Regardless, the war would continue on with Asiagenus raising another army in defense. This time he moved after Pompey, but once again, his army abandoned him and went over to the enemy. As a result, desperation followed in Rome as the year 83 came to a close. The Senate re-elected Cinna's old co-Consul, Papirius Carbo, to his third term, and Gaius Marius the Younger, the 26 year old son of the great general, to his first. Hoping to inspire Marian supporters throughout the Roman world, recruiting began in earnest among the Italian tribes who had always been loyal to Marius. In additional counter measures from an intimidation perspective more blood shed against possible Sullan supporters took place. The urban praetor L. Junius Brutus Damasippus led a slaughter of those Senators who seemed to lean towards the invading forces, yet one more incident of murder in a growing spiral of violence as a political tool in the late Republic.
As the campaign year of 82 BC opened, Carbo took his forces to the north to oppose Pompey while Marius moved against Sulla in the south. Attempts to defeat Pompey failed and Metellus with his African forces along with Pompey secured northern Italy for Sulla. In the South, Marius gathered a large host of Samnites who assuredly would lose influence with the anti-popular Sulla in charge of Rome. Marius met Sulla at Sacriportus and the two forces engaged in a long and desperate battle. In the end, many of Marius' men switched sides over to Sulla and he had no choice but to retreat to Praeneste. Sulla followed the son of his arch-rival and laid siege to the town, leaving a subordinate in command. Sulla himself moved north to push Carbo, who had withdrawn to Etruria to stand between Rome and the forces of Pompey and Metellus.
Indecisive battles were fought between Carbo and Sulla's forces but Carbo knew that his cause was lost. News arrived of a defeat by Norbanus in Gaul, and that he also switched sides to Sulla. Carbo, caught between three enemy armies and with no hope of relief, fled to Africa. It was not yet the end of the resistance however, those remaining Marian forces gathered together and attempted several times to relieve Marius at Praeneste. A Samnite force under Pontius Telesinus joined in the relief effort but the combined armies were still unable to break Sulla. Rather than continue trying to rescue Marius, Telesinus moved north towards Rome. Sulla raced after, not wanting to give up an opportunity to win the war and claim the ultimate prize right outside the gates.
On November 1 of 82 BC, the two forces met at the battle of the Colline Gate, just outside of Rome. The battle was a huge and desperate final struggle with both sides certainly believing their own victory would save Rome. Sulla was pushed hard on his left flank with the situation so dangerous that he and his men were pushed right up against the city walls. Crassus' forces, fighting on Sulla's right however, managed to turn the opposition's flank and drive them back. The Samnites and the Marian forces were folded up and broke. In the end, over 50,000 Romans lost their lives and Sulla stood alone as the master of Rome with the following sunrise.
In a meeting the following day, and while the execution of several thousand prisoners was taking place, Sulla addressed the Senate in the temple of Bellona. Here he began to lay out the law that would eventually re-shape Roman government, at least for a time, and show the Senate what Sulla's vengeance would mean. Just as the proscription of his political enemies was about to begin, however, there were still matters to deal with outside of Rome. The siege of Marius in Praeneste continued, and Sulla needed to put an end to it to take final control.
The man recently responsible for the death of his supporters, Damasippus, was beheaded for a special purpose. In order to show Marius that Sulla now had Rome and was the victor, he had the head thrown into Praeneste as proof. It wasn't long before Marius realized that all was lost and ordered a slave to take his life. All was still not over for Sulla, however. He unleashed the young Pompey (whom later was possibly dubbed Magnus "the Great", somewhat sarcastically by Sulla), on the countryside and any remaining opposition. By 81 BC, Pompey captured and executed Carbo and the son-in-law of Cinna, Cn. Domitius Ahenobarbus. He then brought Africa under the control of Sulla and the resistance was over. Sulla was now the undisputed ruler of Rome.