The Greek cities of southern Italy called on King Pyrrhus of Epirus to protect them from Roman encroachment. Though Pyrrhus was undefeated in battle, his victories were so costly that he was forced to withdraw from Italy in 275 BC, leaving Rome in control of Magna Graecia.

Rome battled a combined army of Samnites, Etruscans, Umbrians and Gauls for control of Italy. At Sentinum, the two sides fought the largest battle in Italian history up to that point.

After a five year break, hostilities resumed between the Romans and Samnites. Despite early setbacks, Rome eventually emerged victorious in 304 BC. During these years a controversial politician, Appius Claudius, initiated a series of ambitious public works projects that advanced Roman civilization.

After a decade of peace, the Romans and Samnites returned to war. The early years of fighting went well for Rome, but in 321 BC they were handed a humiliating defeat at Caudine Forks.

The Roman army abandoned the Greek phalanx in favor of a new system based on a three line deployment organized by age and experience.