If you want a good study of military history and mythology you can look at the Greek Persian wars and how they affected the entire world at that point. You could also have a look at the Romans and talk about how they would conquer lands, adopt the cultures and religions, and use that to assimilate those people into their kingdom (for example the similarities between the Greek Gods and the Romans, and how Christianity was developed in Rome while Christ himself was Jewish) how that ultimately became one of the reasons the empire collapsed!