They couldn't say that the Soviets had acoustic means of picking up American submarines, because they couldn't find it. So they said, well maybe they have a non-acoustic means of making our submarine fleet vulnerable. But there was no evidence that they had a non-acoustic system. They’re saying, 'we can’t find evidence that they’re doing it the way that everyone thinks they’re doing it, so they must be doing it a different way. We don’t know what that different way is, but they must be doing it.
Rumsfeld and Cheney Revive Their 70's Terror Playbook