Hernando Cortez burned his ships to make a point with his men that it was conquer or die. Do you really see a Marine Colonel going all-in like that? Modern values kind of mitigate against wholesale slaughter. Even if he were to give such an order the Marines might hesitate to engage in wanton killing. Unless of course everybody "got their mind around the situation". (Realized that they had little choice).
I was just tossing out a wildcard. My point was that a single modern military unit just doesn’t have the number of rounds for guns, armor or artillery to take on a nation.
My point was the ONLY way a modern military unit could take over an ancient nation would be IF that nation surrendered to the invading “gods”. I just used the example of Cortez to give historical precedent for it.
This is all just hypothetical and I was tossing in my brain-stormed 2 cents.