(340–338 BC) was a conflict between the Roman Republic and its neighbors the Latin peoples of ancient Italy. It ended in the dissolution of the Latin League, and incorporation of its territory into the Roman sphere of influence, with the Latins gaining partial rights and varying levels of citizenship.
A push by the Latin people for independence from Rome was the main impetus for starting the war. In 340 BC, an embassy was sent to the Roman Senate to ask for the formation of a single republic between Rome and Latium, with both parties on the same level. Since Rome had been, in the previous years, the leader of the Latin League, it refused to put the Latin people on her same level and to accept Latins in the Roman Senate. With Rome’s refusal, the war began. The Romans had been fighting alongside the Latin and Campanian peoples against the Samnites in the First Samnite War when the Romans withdrew from the war. The Latins continued fighting beside the Campanians, while Rome switched sides, joining the Samnites to attack the Latins. Only the Laurentes in Latium and the equites of Campania adhered to the Romans, who on their part found support among the Paeligni.
The Latins entered Samnium; the Roman-Samnite army moved to the Fucine Lake, then, avoiding Latium, entered the Campanian territory and attacked the Latins and Campanians near Mount Vesuvius. In the Battle of Vesuvius, the Romans, under consuls Decius Mus and T. Manlius Torquatus Imperiosus, defeated the Latins. According to Roman sources, Manlius reinstated army discipline by executing his son for his unintentional disobedience, while Decius sacrificed his own life to the gods for the Roman victory.
One year later, Manlius defeated the Latins at the Battle of Trifanum. The Latins, forced to leave Campania, moved to Latium, where they put up a long yet unsuccessful resistance against the Roman forces. The defeated Latin peoples were obliged to recognize Roman pre-eminence. Some of the Latin towns were Romanized, others became partially Roman, adopting Roman magistratures, while some others became Roman colonies.