The year was 220 B.C. and the young Carthaginian general Hannibal Barca had to return to his winter quarters in Qart Hadasht - now Cartagena in southeast Spain - after taking Helmatica - now Salamanca in the northwest of the country - from the Vettones tribe. It was spring or summer, and the 27-year-old and his troops had to overcome two obstacles to get to their destination: firstly, the wide rivers and high mountains that were difficult for their 40 elephants to cross; the secondly, the hostile local Carpetani, Vettone and Olcade tribes, who sought revenge for the destruction of...