Umm I hope this isnt news to you since you have been fairly active in the WW2 thread but the "enemy" isn't going to show up as a horde on horse back with 200,000 infantry and a bunch of elephants, that pretty much died withthe last Iranian agression in 480BC which oddly enough seems to be about where your thinking stopped on this one.
Lets look at ISIS for example they are apparently the biggest threat out there and they claim 200,000 strong where as the CIA claim they are maybe 35,000 strong other numbers I have seen put them around 80,000 but lets assume they are not making things up and they are 200,000 they lack professionalism, they lack a ready supply of heavy weapons, they lack any meaningful communications systems and logistics capability and most of all they lack secure allies all the things a modern army and nation has.
Therefore I fully expect that should this "horde" come steaming out of the desert on their Toyota Camel 4x4 even your 25,000 Belgians would make short work of them.
Outside that I would argue your thinking is outdated at the very least and that modern nations are no longer looking at wars on a long term nation v nation scale but rather short regional wars against insurgencies and oddly enough to defeat terrorism at home you don't need an army you need a stable political system and a content populace and to defeat terrorism abroad you use far smaller numbers of troops.
Now to upset the Americans a little (somewhat unintentionally) but it is American thinking that is out of sync with the way the world is going they spend trillions on a military to defend a nation that is geographically unattackable on a scale that requires a military the size of the US therefore it is geared toward force projection in a world that no longer needs it consequently US foreign policy is geared towards creating an enemy in order to justify its military spending.
No offense guys.
