[pc86]

If you have limited resourced (no money), but you do have military power, you can invade a neighbor with resources. If a neighbor invades you, you defend yourself.

Neither of those positions is irrational, except maybe the first (maybe), but there's certainly scenarios where it would be your only choice.

[throwaway316943]

It becomes irrational when you develop the capacity for mutually assured destruction.

[omginternets]

MAD is grounded in game theory. It is designed to make the only winning move “don’t play”.

It’s hyper-rational.

[DaiPlusPlus]

MAD happened because of a (real, or perceived, I’m unsure myself...) risk of the Soviet Union invading Western Europe - and NATO ended up calculating that maintaining a nuclear deterrence was more affordable and more feasible than resisting a Warsaw Pact invasion using conventional forces. This assumes any kind of Soviet expansionism must be an absolute evil because the position is logically equivalent to “death is a preferable alternative to communism” (to steal a phrase from a video game...) which is patently absurd: it’s rational to prefer reduced standards of living over death, but credible deterrence requires drawing and maintaining a hard-line, even if that line is arbitrarily placed.

...given all of that is due to the risk of aggression from the Soviets, and I believe NATO may have disarmed themselves unilaterally if they didn’t see the SU/WP as a military threat (regardless of ideological threats) - what was making the SU so concerned about NATO military threats? Did the SU still have expansionist designs... or did they actually believe NATO still wanted to liberate/claim Poland long after the 1960s?

[omginternets]

I respectfully insist: you are mistaken.

MAD is a formal (i.e. mathematical) model. It is 100%, unequivocally rational. The problem is that this rational process leads to outcomes you and I dislike.

These "bad outcomes" are value judgements. That is, MAD's outocmes don't align with our values. Therefore, the problem with mad (on which we agree!) is based in something extra-rational: values.

Again: you and I agree there is a problem with MAD. Where you are wrong is that the problem is not "MAD is irrational". The problem is "MAD's logical conclusions run afoul of our values".

[squeaky-clean]

Mutually assured destruction on a planetary scale does come about rather early in a civilization's history (if we're assuming galactic, or beyond-galactic scales of civilization). But that doesn't really mean it is easy to come about on a galactic or universal scale. Is an enemy destroying a planet or solar system you control really such a big deal when you're battling to control a third of the universe? Even having an entire galaxy destroyed would be like an enemy destroying someone's living room on an earth-scale.

Of course, this is all just making guesses about technology way beyond our current comprehension. Maybe universe-destroying bombs come up rather early in technology on this scale. Who knows.