I mean, I’d hope so, since marching through Belgium is how Germany got the UK drawn into WW1. Attacking neutral countries is a good way to get other neutral countries involved.
There’s a lot wrong in this quote, starting with the apparent belief that Vatican City and Monaco are EU members.
Maybe it’s just me but Belgium seems a lot more substantial than Andorra.
The point I’d that the actual fighting in Belgium was barely a speed bump to the Germans, but pulling in the British - with their expeditionary force, their colonial reinforcements, and their mighty navy - was disastrous. (The German surface fleet is often dismissed, but had Britain not gotten involved in the First World War, the German fleet would have been very capable).
The question isn’t what Andorra’s armed forces can accomplish. It is who is guaranteeing Andorra’s independence. (Or, more cynically, who would love to enter the war on Spain’s side and is looking for an excuse to do so).
And I guess that’s what I was getting at when I wondered what the OP might mean by ‘independent’. If someone else is guaranteeing your independence, just how independent are you, really?
NATO countries don’t, I’m guessing, guarantee one another’s independence through the treaties they entered into. They’re just saying, “I’ll do my best to help if that other guy tries to beat you up.” On the other hand, if you don’t exist except by virtue of your large neighbors’ or enveloper’s benevolence, are you independent for the purposes of the OP?
So, the Low Countries in the first half of the 1900s weren’t really independent?
I think Germany and Italy came together as states only in the 18th century. Of course, Napolean messed everything up and it had to be put together again. Why isn’t Austria part of Germany? Why is Portugal separate from Spain while Catalunya is not? I guess all these answers come down to individual histories.
They came together as states in their modern form in the 19th (not 18th) century (1871 for Germany, 1861 for Italy.)
Since the two co-leaders of Andorra are the bishop of Urgel and the president of France, one of them will be on our side 
By the way in Europe most (actual) small countries are the remnants of accords between various kings,bishops, popes and lords that were not incorporated in the formation of the nation-states in XVIII and XIX centuries.
You see the small white polygone in the south near Nyons? it is an enclave of the Vaucluse in the Drôme departement. Why? because before the 1789 revolution it was part of the Papal State (based in Rome) and was dependent of the town of Avignon located in the Vaucluse. and that dates back to the XV century when there was a Pope in Avignon and another in Rome…
So if you live now in this white polygone, all your administrative stuff depend not of the nearest town but of Avignon, 50 km south and in another departement, all because of guys from 600 years ago…
The question is actually: why should a large country want to invade a small country and have their inhabitants become citizens? it is a lot of trouble, bad for international relations, so you really need a good reason. If there is not enormous wealth or natural resources or some kind of political reason (such as unification of Germany), it is hard to make a good case. There is also something called national sovereignty which states for some odd reason believe to be important.
Why is Puerto Rico not part of the USA? Why did the USA not make Grenada part of the USA after the 1983 invasion? Answer those questions, and you may have answered the OP.
There have been a couple examples of a larger country invading and trying to assimilate a smaller one in fairly recent times:
- Iraq invading Kuwait in 1990. I think we all know how that turned out.
- Indonesia and Timor Leste – invaded in 1975 but eventually Indonesia relinquished control.
Possibly the take over of Macau and Hong Kong by China should also be on the list, although those were technically colonies, not independent countries. Another recentish (1961) colony taken over by a larger adjacent country was Goa, which is now a state within India.
[quote=“Hari_Seldon, post:27, topic:953787”]
Why isn’t Austria part of Germany?[/quote]
Once upon a time most of Germany was part of the Hapsburg-dominated Holy Roman Empire. Thereafter, neither German nationalism nor the increasing dominance of Prussia wanted to take in the whole of the Hapsburg Empire, and when that was dismembered after WW1, German Austria was not allowed to consider joining Germany (and there were plenty of Austrians opposed to the idea too).
Dynastic marriage made Catalonia part of the Kingdom of Aragon. Further dynastic marriage united Aragon and Castile into the Kingdom of Spain. The kings of Portugal, on the other hand, had England as an ally to support them as a counterweight to Spanish power.
Yup. It’s not really until relatively modern times that cultural/ethnic identity began to outweigh dynastic considerations in defining polities/states.
Er, say what, now? 
You are right, I should probably formulate that more precisely. Why is Puerto Rico not just incorporated territory of the U.S.A.?
In Puerto Rico, the pro-statehood and pro-independence factions usually boycott each others’ polls. In the last poll which everyone agreed on (several decades ago), the “independence”, “statehood”, and “status quo” sentiment was about evenly divided.
Because Puerto Rico can’t make up its mind whether it wants to be a full blown US state or not.
Dammit, ninja’d!
The real question on Puerto Rico is: Why didn’t the US give them independence like it did for Cuba and the Philippines? I’m talking about back in the first half of the 20th century, not now. There was no Statehood movement back then, but there was an Independence movement.
But per the premise of the OP the rest of the USA could simply decide to ignore the wishes of the population of Puerto Rico and decide either to incorporate it into the USA, or alternatively cast it off and leave it to its own devices. The fact that the USA (quite rightly) does not take either course without involvement of the population goes some way to answering the question why large countries don’t just take over small countries.
Tell that to Hawaii.