This is inspired from Rome Sweet Rome. It is a story about a marine platoon(or something) suddenly finding themselves back in time, during the first years of the Roman Empire, under Augustus. This interesting concept took birth in a reddit thread that was discussing modern military versus classical Rome. Apparently they are making a movie out of this..though i think an HBO/netflix series would be vastly superior.
I just took the general idea and give it a different spin. There's so little art about that concept.