[graeme]

The thing with defense is that even without the ABM treaty, we don't have an effective defense. MIRVs will always be cheaper than single shot ABMs, and their reliability is too low to rely on in the event of a second strike. That's what I meant by it being a reality.

People do of course adopt it as a strategy as well. But if effective defense tech existed I don't think the strategy would hold. The US abandoned the ABM treaty even without such technology.

As for your first point, it's true that MAD didn't really conclusively come into force until submarines. But there were efforts before then to maintain a second strike capability, such as keeping a certain percentage of bombers in the air, preparing them for fast takeoff, etc

Maybe not 100% assured second strike, but the basic idea was the same