The republic came into existence in Rome in the aftermath of the sack of the city by forces from the Gallic Empire, which was at that point fighting for independence from the Roman Empire. The sack resulted in a power vacuum. Several factions sought control of the city, one of which was a republican faction. Ultimately, the republican faction prevailed. A new Senate was elected, and it immediately elected two Consuls and proclaimed the Second Roman Republic. The new republic expanded into the surrounding area over the following months, as republican factions gained control of other towns and cities that had been devastated during the Gallic invasion of Italy and declared themselves loyal to Rome.
What ultimately led to the downfall of the Second Roman Republic was that the republican movement began to spread too quickly into the territories that had been controlled by Asclepiodotus and Probus. In June 276, both claimants to the Roman throne launched campaigns to conquer the Second Roman Republic and its allies. The Second Roman Republic was no match for the Imperial armies, and was fully conquered by July 4, 276.