In short, the Roman Republic did not demand Hannibal’s detainment or execution after the Battle of Zama in 202 B.C because he was no longer viewed as a threat.
Every general needs an army. At Zama, the last dreg of Carthaginian manpower was destroyed, with most of Hannibal’s force being destroyed. Livy (Book XXX.37) indicates that one of the peace terms dictated by Rome was that Carthage could not wage war on any nation without prior Roman permission, whilst Robin Lane Fox mentions that the state was required to hand over all war elephants to Rome, additionally swearing to never train any more of them (‘The Classical World’, pp.328).
Livy has an insight on this. Though he injected drama into his work, he did base it off the work of Polybius which gives it some merit as a source. The following quote is from Book XXX , occurring in the Carthaginian Senate after Rome’s terms of peace have been read aloud after the Battle of Zama:
Section 35:
“Before the Senate (Hannibal) admitted that this defeat in battle was also total defeat in the war. He saw no hope for the future unless Carthage asked for terms of peace and was granted them.”
Here, Livy signals that Hannibal has accepted the war has been lost, and has no desire to continue the war.
Section 37:
“(Carthaginian Senator) Gisgo came forward to oppose the peace…until Hannibal could bear it no longer…and pulled Gisgo down from the platform with his own hands.”
“After this… he spoke at length about the peace, showing that is was far from unfair and must be accepted”.
This quote is crucial to my view on why Rome spared him; On the surface, he became a supporter of peace with Rome. If Rome chose to seize him, it would polarise opinion against Rome on an already unpopular peace treaty. Rome wished to maintain peace with Carthage after the war (rather than destroying it) as they were scheduled to pay 10,000 Talents of Silver over 50 years in war reparations (Book XXX .36).
Note this tribute had coincidentally just been paid off when Rome decided to raze Carthage to the ground in the Third Punic War.
Sources:
- Livy, ‘The War with Hannibal’, tr. Aubrey de Selincourt, Penguin Classics (1972)
- Robin Lane Fox, ‘The Classical World’, The Folio Society (2013)