Through the course of the campaign of 82 BC, the Populares forces had divided into two groups, those in the north under the command of Gnaeus Papirius Carbo, and those in the south who were commanded by Gaius Marius the Younger. Sulla had successfully defeated Marius Battle of Sacriporto and had managed to pin Marius and his fellow survivors under a siege at Preneste. Rome itself soon after had fallen to the Optimates. Soon after, the war had shifted to Etruria where Sulla engaged in a pitched cavalry skirmish against Popular forces near the Glanis River, emerging victorious.
According to Appian, the two armies eventually met on the outskirts of Clusium. After a bloody battle, the armies separated at nightfall. The battle is generally referred to as a stalemate, but the Germanscholar, Theodor Mommsen affirmed the following:
The battle remained indecisive, however, Carbo gained a clear advantage as he detained his adversaries' march. - Theodor Mommsen
The surviving Populares forces, including Marius, took refuge at Preneste to escape the pursuing Sullan forces. Sulla arrived shortly thereafter and besieged the city. The city fell on 4 November, holding out surprisingly until all of Italy was under Sulla's direct control.