The more you become familiar with the history of those conflicts, the easier this task will be. Certainly you need to mention Rome's reverse engineered navy, it's adaption of tactics for marine battles, Hannibals strategies and successes in battles, the muddled strategy, poor battle results, and inherent organisation problems of the Roman forces weighed against their ensuing Fabian strategy and available manpower. People in Rome thought that after Cannae all was lost. They panicked, convinced that Hannibal was within a few days march of ssacking Rome. Why didn't he? Why did he fail to land a final blow in his Italian campign? Elephants, however dramatic, were insiginficant in the long term as only a few made it across the Alps and disappear in the record shortly after. Consider the theatres of war - Spain, Africa, Italy, and elsewhere.