And how is that even remotely just? You're holding all of the citizens of the country responsible for the actions of a few stupid people in power.

That would be too late, wouldn't it.
Besides, I don't think nuclear warfare is a solution to this.
Just because the US has enough nuclear weapons to destory the world several times over, doesn't mean it is in the country's best interest to annihilate another country.

Rather, they're used as a threat (I forget the actual word :(), right?

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The question is, what happens when N. Korea, who have all these bombs, and ordered by their crazy leader, to start a war with America because they've been itching for it for so long?

What would the best course of action be - pre-emptive, such as was the excuse with Iraq, or retialitive (look ma, I made a new word!), attacking only when Alaska has been decimated?

Is it right to kill a few thousand to save 320 million?

Balance of terror? Unfortunately, one of the few strategies to win an all-out nuclear war is to almost annihilate the entire world, and ensure that whoever launches the next nuke will obliterate humanity with radioactive contamination. There will then be little incentive for the "losing" side to retaliate. Of course, this strategy is not very practical, since it's difficult to determine the exact amount of radioactive contamination required to end the human era. (Obviously, underground shelters are not taken into account.)

Strategy for victory: Always use pre-emptive strikes against nations and unions with inferior technology (such as North Korea) before they use WMDs and/or catch up with us. Focus most of your resources on trade and research. Make the proletariat accept increasingly limited freedom in favor of security. Offer them opportunities to oppose changes (e.g. via voting) that have no actual impact on the progress. Ensure that the majority thinks that they're fighting for the right side through arbitrarily defined incentives (such as money). Out-tech everyone else and become untouchable.

We'll be Gods among men in our virtual prisons!

I thought it was
Mutually Assured Destruction

Balance of terror takes other WMDs into account as well, such as ones of the biological warfare class.

Destruction is destruction regardless of form.

Do you mean deterrence?

One reason for having nukes is to deter adversaries from using that and sort of having a sense of security and defense. Even for North Korea and Iran, one reason why they desire for nuclear power is that they want to be safe from US and Israel.

I still believe in diplomacy concerning this.

As for the question, is it right to kill a few thousands to save 320 millions, I think it is not really the right way to look at it. Also, you question is really, is it right to kill a few thousands innocent because there are some reasons believe that they would cause harm to millions..