Why did Roman people joined Hannibal and his armies?

Hasdrubal, recognizing that Spain was a lost cause, crossed the Alps to join Hannibal in Italy for a united attack on Rome. At the Battle of the Metaurus River in 207 BCE, however, Hasdrubal's army was defeated by the Romans under Gaius Claudius Nero (c. 237-199 BCE); Hasdrubal was killed and his forces scattered.

Explanation:

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