Final answer:
Hannibal began with 60,000 men when crossing the Alps into Italy; however, exact numbers of survivors are not provided in historical records. The challenging conditions led to substantial casualties, both for his army and in later historical events such as Alpine warfare during World War I.
Step-by-step explanation:
The journey through the Alps by various groups over history has been a significant challenge, resulting in many casualties. In the case of Hannibal's crossing, which is a notable historical event, he started with 60,000 men, but we do not have an exact count of how many survived the journey itself. Historical accounts indicate that he suffered substantial losses during the crossing and in the ensuing battles with Rome. The reference to an 80% death rate in settlements around Chiavena during an Alpine crossing, related to a plague outbreak, suggests a high mortality rate, but this does not directly answer the question about Hannibal's troops. Moreover, accounts of World War I battles in the Italian Alps mention more than half the casualties due to poor conditions rather than combat, highlighting the dangerous nature of Alpine warfare.