Something that doesn't often get remarked upon is that the Cold War wasn't the first instance of the strategy of MAD. World War 1 was the culmination of a MAD strategy gone awry.
How did World War 1 involve mutually assured destruction? It seems to me that destruction can't have been particularly strongly assured given that the significant powers on one of the sides wasn't destroyed. There were significant casualties and economic cost but MAD tends to imply something more than just "even the winner has casualties!" considerations. Are you using "MAD" far more loosely than I would expected or making some claim about history that surprises me?
(By contrast a Cold War in which both sides had lots of nuclear weapons stockpiled actually could result in mutual destruction if someone made a wrong move.)
Far more loosely. Part of the object behind the complex network of alliances was to make war too costly to initiate. Once war was initiated, however, it was guaranteed to be on a massive scale. The damage done by WW1 is forgotten in consideration of the damage done by WW2, but it carried a substantial toll; around 33% of military-age British men died over a four year time period.
In both cases the nations involved were always one event away from total catastrophe.
The standard view of Mutually Assured Distruction (MAD) is something like:
Occasionally people will reply with an argument like:
This is an anthropic argument, an attempt to handle the bias that comes from a link between outcomes and the number of people who can observe them. Imagine we were trying to figure out whether flipping "heads" was more likely than flipping "tails", but there was a coin demon that killed everyone if "tails" came up. Either we would see "heads" flipped, or we would see nothing at all. We're not able to sample from the "tails: everyone-dies" worlds. Even if the demon responds to tails by killing everyone only 40% of the time, we're still going to over-sample the happy-heads outcome.
Applying the anthropic principle here, however, requires that a failure of MAD really would have killed everyone. While it would have killed billions, and made major parts of the world uninhabitable, still many people would have survived. [1] How much would we have rebuilt? What would be the population now? If the cold war had gone hot and the US and USSR had fallen into wiping each other out, what would 2013 be like? Roughly, we're oversampling the no-nukes outcome by the ratio of our current population to the population there would have been in a yes-nukes outcome, and the less lopsided that ratio is the more evidence that MAD did work after all.
[1] For this wikipedia cites: The global health effects of nuclear war (1982), Long-term worldwide effects of multiple nuclear-weapons detonations (1975). Some looking online also turns up an Accelerating Future blog post. I haven't read them thoroughly, and I don't know much about the research here.
I also posted this on my blog