Which is why, during the Cold War, the US maintained very powerful long wave transmitters, both land-based and airborne. Using VLF†, they could send the nuclear launch codes to the nuclear missile submarines without the subs having to break the surface and create a possible radar return.
They kept an airplane aloft 24 hours a day carrying a SAC general. In the event of war, it could reel out a long-wire antenna a couple of miles long from its tail and send out the codes.
According to the Wikipedia†, the aircraft in question had a 200 kw transmitter, but the article is a bit vague about VLF in particular.
The idea, of course, was that while, hopefully, the ground stations would get the message out, there was that airplane you couldn't count on knocking out in a first strike.
http://en.wikipedia.org/wiki/Extremely_low_frequency