America is a land of immigrants. It would not be at all surprising if one or more
members of a MEU grew up in a house where they spoke Greek at
home. I would be extremely surprised if none of the Marines
had studied Latin. Many Marines would speak
Spanish and probably could learn Latin quickly. But really that does not matter.
To say the Marines couldn't use psychological warfare without understanding the language is completely wrong. Psychological warfare is using all aspects of psychology to achieve
victory. We are not talking pamphlets and radio broadcasts. The most important use of psychological warfare in this scenario would be to demonstrate power so overwhelming that it would not be challenged. It would take very little of a MEU's resources to do that. For example, firing a single shell taking down a city wall would probably be enough to make an ancient city surrender (only gods could do something like that). Even if one shell was not enough, how much more would it take? A sniper shooting a few people in the
head? Would it take more? How many booms and dead people could it possibly take? After the first few cities, the rest would know the Marines were coming before they arrived. The gates would all be wide open when they arrived.
They might not be able to maintain their existing vehicles or
weapons in the long run but they certainly would be able to make vehicles and
weapons that they could maintain. And we are not talking black powder and muskets either.
My daughter just made batteries for her science project. She is 10 years old. Other kids in her class made generators and radios. All were made from objects easily obtainable in ancient
Rome.
Don't underestimate the Marines because they have not been entirely dominant in modern times against insurgents and guerrilla warfare. The capability of the Marines in modern warfare is restricted by morality, concern about winning hearts and minds, about right and wrong, and by concern for sparing innocents. Without those restrictions, modern insurgents, in Afganistan for example, could be utterly exterminated and their support utterly destroyed...and they have guns.