Hannibal's descent into Italy began after his difficult crossing of the Alps in 218 BC. Having overcome harsh conditions and attacks from local tribes, Hannibal and his remaining troops descended into the fertile plains of Northern Italy, near the Po Valley. This marked the start of his Italian campaign during the Second Punic War. Hannibal’s arrival caught the Romans by surprise, as they had not expected him to successfully cross such insidious terrain with his army, elephants and supplies.