- You behave diplomatically in a way that takes into account an active missile defense. Attack happens where it would not if you had followed a more moderate policy. Defense does not work after all.

No missile defense, even the best hypothetical one, is perfect. No sane politician would provoke an ICBM attack from a nation so armed, defense or no defense. And if the defense, as stipulated, is much less than perfect, this is even more insane. If you have such a person running the country, the missile defense or lack thereof is the least of your problems.

- Opponents think you have a missile defense, so they counter by building more missiles than otherwise.

If you have no missile defense at all, they don't have to build more, do they? A missile launched is a city destroyed. Why is that a better scenario? It's throwing uncertainty into this equation that makes all the difference. A nation like North Korea cannot easily double the number of ICBMs in its arsenal, never mind the warheads. This arms race against the idea of missile defense is part of what drove the U.S.S.R. into bankruptcy.

And an imperfect defense in this case kills nobody, unless they were going to attack anyway.

- opponents think you have a missile defense, so they contrive to get their nukes off of missiles and onto shipping containers instead. Spend all the money they save on missiles, buying more nukes.

If shipping containers were the ideal attack method, the U.S.S.R. would have used them. Again, an ineffective missile defense kills no more people in this case, and then only if your enemy was going to attack you anyway. Note that absolutely no missile defense does not make an attack by shipping container any less likely. A missile defense at least limits the options. Just because someone might shoot you in the head does not make a bulletproof vest useless.

Money saved on missiles spent on nukes? These guys shopping at WalMart?

- Opponents think you have a missile defense, so they start looking at ways to base their missiles closer to your shores on shorter range missiles, or cruise missiles, or motorboats or whatever.

They're welcome to try. There are a LOT of military folks looking for just this sort of thing. Or do you think the North Koreans will be sneakier than Soviet attack submarines?