In the modern day a isolated country with no standing army (and no military agreements with other countries with a military) is invaded. The country in question has similar characteristics to Iceland (minus the military defense agreement with the U.S.) This country has no standing army or major paramilitary force that could pose a threat to the invading enemy army and has not for the last one hundred years (unless you take the lightly armed police and coast guard.) Firearm legislation allows for all citizens to be able to own handguns as well as shotguns and rifles, but few do.

Now the invading enemy army...

Where has this army invaded?

Assuming Iceland is our model country, the enemy force has attacked from the western most point.

How large is this enemy force?

Around 20,000 strong (two divisions.) They are mainly infantry armed with AK-74s and russian body armour. They also have a 500 strong logistics and communications brigade and a mobile AA squadron (with a dozen SA-6s.) There is also a small number of armoured personal carriers (APC) and Tanks; probably T-72s and BMP series APCs (up to 50 APCs and 20 tanks.)

How long until they reach the capital (in the east of the country)?

Two weeks at the most, due to rough terrain that bogs-down their wheeled vehicles.

Question

How can a country with no standing army for the last one hundred years mobilize an army?

Additional Question - Would the defending country's government be able to appeal to the UN or NATO for support/an expeditionary force?

They can't.

A modern day army, with that kind of strength, would wipe out any main (police) resistance pretty fast. Assuming they prepared it somehow, and not just you know, discover that there's some land there and have no idea how to go around.

The main reason for it, is not necessarily the lack of army, but mostly the lack of equipment.

Let's see how that could go down:

1. The invasion begins (and they did not use air planes, or artillery to cut any communication mean, just because.


2. The government gets to hear about it. And decides to mobilise the troops to resist the invasion (because they can be irresponsible as well).


3. They somehow contact the population (with the communication that still wasn't cut, remember?) like with SMS/Email.


4. People rally to the designated centres (because they are patriotic/suicidal) and somehow the invading army does not get to know about that, observing many people moving to a specific destination.


5. They give them the best they have: a set of police equipment: rifles, guns, some helms, etc. (This is assuming, their police was well funded and had that much surplus).


6. They train them (meaning, they give them a chance to shoot, if they don't die trying, then good enough, they can join the front).


7. The first mobilised troops get to face the invasion (who were kind enough to wait for them to come up).

They are now equiped with some shields, light guns, and maybe gas grenades... to face tanks.

The Russian (in)famously faced the German army on such similar imbalance. But first they needed time to gather their troops, and had to fall back a few thousands of km first. On Iceland's scale, that's the sea. And they made it work by having a much more populated army. Iceland has 380,000 inhabitants. You don't get the 60-80,000 stronged-troup in 2 weeks. And modern weapons are slightly more effective than WWII's.

Altenatives

I can see two alternatives.

• They were in the situation you described, realise that they have no chance, and surrender. However they try to arm and organise some resistance. When there's such a strength imbalance, guerilla's tactics are the go-to choice.




• They were not completely irresponsible and had a plan put in place to defend themselves. Which, I guess most evolved countries do. Either they train their citizens regularly (like Switzerland), or they have agreements with stronger countries, etc. And put the plan they had into place.

Same way small countries without standing armies do now. The police are used and added to. Many small nations police are specifically sent on peace keeping missions so that they can learn some military type skills.

Would the defending country's government be able to appeal to the UN or NATO for support/an expeditionary force?

They could appeal to anyone they want or pray even. But it's totally dependent on political expedience and economics on whether they get any help or not. Iceland being basically part of Europe would get quicker more effective support than somewhere like Tonga. PNG has been appealing to everyone in sight, yet despite being next door to Australia receives no help from an invading modern army practicing genocide.

In practical terms without treaties with other countries they're pretty much on their own.

They don't need to mobilize an army?

Even without the military, the US would be a hard country to invade. The general population is nationalistic and there is easy access to guns and ammunition. There is also a number of gun enthusiasts with reasonable training that could manage and train smaller fractions of resistance. This is hard to fight against as an invading force...

Iceland has a population of around 350 thousand people. If slightly more than 10% decided to try and sabotage the invading army, you'd get twice the number of guerrilla soldiers as the invading army. If they're nationalistic or the invading force is cruel, they can get significantly more. That's going to put a damper on the invasion real quick.

They might not have a standing army, but there is nothing to say they can't have resources available. A emergency stores with supplies such as medicine, food and water could go a long way. If there's some weapons and ammunition available, that would be great. For that sake, there is nothing to say that the country itself isn't a big exporter of weapons.

Secondary question: Yes they can ask whoever they want. If they will get help is another question.

Long and short, two weeks isn't really long enough for many plans. We should have been gearing up to defend ourselves before anyone ever arrived, but we can't change the past.

In the position of the not-icelandic government, my first move would be to hire a substantial paramilitary mercenary group to help defend my nation. Our biggest military resource right now is probably our wealth.

My second move would be to form a militia and arm them. If there aren't enough weapons to go around, that's a limiting factor since any competent invader will have blockaded us. As other answers have noted, Not-Iceland has a heck of a lot more people than the invading army, if even a modest percentage can be armed and equipped and are willing to fight, that's an army of similar size even if it lacks in quality.

Thirdly, I would also be making serious overtures to anyone who might be sympathetic and powerful enough to help out.

Guerrilla Warfare with the support of the population has a long history of success. Take Finland during WW2 as an example. With the assistance of a bitter winter, knowledge of the terrain and a tenacious determination to drive the invaders out, they repelled both the German and Russian armies using a militia armed with hunting rifles.

You mention that citizens are allowed to have weapons, but few do. However, the fact that they can means there's a supplier of firearms. If everyone in the capital purchases a weapon and the police force starts organizing a paramilitary style army for two weeks, they could at least put up a fight. If they demolish the roads leading to the capital, set traps everywhere and engage in extended urban warfare they could last a couple of weeks at most. Maybe that's enough for reinforcements from other allied nations to arrive?