The rise of Rome was far from inevitable. As the Romans moved to secure their control of the Italian peninsula, another people, the Carthaginians were busily establishing their own empire in Spain and North Africa. It was inevitable, however, that the two rising powers in the region would clash violently at some point: there simply wasn't enough room arround the shores of the Western Mediterranean for two empires to coexist.
Fortunantely for the Carthaginians, they were blessed with a great general in Hannibal, who can only be described as a military genius. In 218 BC he led a force from Spain, over the Alps and into Northern Italy to directly challenge Roman power. He defeated the Romans at Trebia in 218 BC and forced them onto the strategic defensive.
Hannibal continued to push hard, and found a Roman army at Lake Trasimene. Now he would have another chance to prove his worth, this time against the full might of a consular army under C. Flaminius. He had already demonstrated tactical finesse in commanding many different types of soldiers against the relatively brute force aproach of the Roman commander at Trebia. Now Hannibal intended to teach the Romans another hard lesson. It was not to be the last lesson in generalship he would hand out.