Good question! The rules don't account for different generals. Of course, "Foresight' is based on Hannibal's strategic brilliance.
I suppose when you play your tactically clueless friend you can call him "Varus" and your ruthless friend could be "Scipio."

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And to whet your appetite a bit more for Alexander & Persia, there are 3 generals in the Alexander faction (Parmenion, Nikanor, and Alexander himself). They show up in the form of replayable command cards.