Between the years 508 BCE and 351 BCE, Rome bought a series of wars with the Etruscans. Rome fought one or two of the Etruscan cities at a time.
These wars are successes for Rome. It also fought e its other neighbors. But to the Romans, the Etruscans are different. Rome now considers the Etruscans its greatest enemy.
With each victory, the Romans are more vicious to the losing Etruscans. After all, the Romans thought the Etruscans were vicious to them. Now, as the Romans got the upper hand, they decided to be even more vicious to the Etruscans in return.
By the end of the wars, the Etruscan people stop existing. The Romans simply kill them all. Eliminating them from the land of Italy is the perfect solution to their problem with these people. No more living Etruscans -- no more Etruscan problem.
The Etruscan wars showed how ruthless the Romans are willing to be. It acts as a warning to other neighboring city states. Don't mess with Rome. Don't tick off Rome.
The Romans will use their reputation for ruthless in dealing with other city states. It becomes part of their foreign policy. It becomes part of the war plans.
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