The battle and siege of Capua of 343 B.C. triggered the First Samnite War (343-341 B.C.), the first of three wars between Rome and the Samnites.
The fighting began when the Samnites, a confederate of hill tribes from the central Apennines, attacked the Sidicines, a smaller tribe on their south-western borders. The Sidicines asked for help from their neighbours in northern Campania, an area dominated by the city of Capua.
The Campanians sent help to the Sidicines, but suffered a defeat on Sidicini territory and were forced to retreat. The Samnites followed, and took up a position on the Tifata hills, overlooking Capua. A second battle followed on the plains between Capua and the hills. Once again the Campanians were defeated, and were forced to retreat into Capua, where they were besieged by the Samnites.
After this defeat the Capuans sent envoys to Rome asking for help against the Samnites, who at this point had a treaty with the Romans. According to Livy the Romans were unwilling to intervene militarily against one of their allies until the Capuans surrendered themselves to Roman authority. This meant that the Samnites were now attacking Roman territory, and when they refused to withdraw from Campania war was declared.
The Romans sent two armies against the Samnites. One, under Valerius Corvus, was sent into Campania, winning a victory at Mount Gaurus, to the west of Naples, and thus some way to the south of Naples. After the battle the Romans occupied the Samnite camp, and the people of Capua came out to congratulation them. It isn't clear from Livy if it was the victory at Mount Gaurus that forced the Samnites to lift the siege, or just the approach of a Roman army.