Capua corrupted Hannibal. Luxury and self-indulgence will ruin anyone. Hannibal was everywhere victorious over the Romans till he took up his winter quarters at Capua, the most luxurious city of Italy. When he left Capua his star began to wane, and, ere long, Carthage was in ruins and himself an exile.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894