Blueskies wrote:

One thermonuclear device going off at say 100,000' will wipe out
communications over a very wide area.

A lot of the EMP damage comes from the impulse generated over long cables.
Fiber obviously lacks this problem.

Still, there are other issues (even if we ignore the policital backlash of a
US President EMPing the US {8^). For one, we'd lose a lot of our orbital
traffic (are the GPS satellites hardened against EMP?).

Scientific American did an article on this subject not too many months back.

- Andrew