Hannibal determined from the outset of the Second Roman War, if not earlier, on an offensive policy of taking the war to Italy. It was further argued that this policy allowed for two alternative--but not mutually exclusive--strategic options. One option was a direct descent on Rome with the intent of taking the city; the other was a political strategy of dismantling the alliance system in Italy that was the basis of Roman resources and power.
It was further argued that the latter was evidently Hannibal's option of preference, since after Cannae, when the Roman field armies were effectively destroyed and the way to Rome lay open, Hannibal chose instead to ignore Rome and concentrate his efforts on the Italian allies. It should be emphasized again that the two strategies were not mutually exclusive; a political attack on the alliance system might be preliminary to a subsequent attack directly on Rome. Nevertheless, at the moment of maximum opportunity, the alliance-fragmenting option is the one Hannibal chose.
The questions thus arise of what precisely that option entailed, and why Hannibal believed it would be more productive than a direct assault on Rome. In a negative sense the answer to the latter is clear enough. A siege would be long and difficult, a point that must have been underlined for Hannibal by his experience in the eight-month effort of taking Saguntum.
However, as an argument against a direct-assault strategy, the foreseeable difficulties of a siege were purely relative; they were sufficient cause to reject that option only Hannibal had reason to suppose that a strategy of attacking the Roman alliance system would yield results more quickly or more reliably than a siege of Rome. That is, he must have assumed that operations undertaken to break up the alliance system would either render a siege unnecessary, or improve the prospects of success in a siege at some later date sufficiently to justify t...