[marktwain]

I do not believe one nuclear warhead could do it.

Maybe three or five, if deployed optimally.

The good news is that no one knows for sure.

If you knock down the grid and mass communication for a year, over nearly all of the U.S., then 90% casualties are likely.

Doing that looks to be pretty hard, impossible to predict, and becoming less likely by the day.

One of President Trump’s first acts on taking the job was to look to lessen the potential for castastrophe from an EMP or massive sun flare event.

It would not take that much to harden most infrastructure for either event. Likely a few billion dollars.

President Obama refused to do it.

[central_va]

If you knock down the grid and mass communication for a year, over nearly all of the U.S., then 90% casualties are likely.

Ridiculous. You can't possible believe that?

[LambSlave]

If you knock down the grid and mass communication for a year, over nearly all of the U.S., then 90% casualties are likely.

You seriously underestimate your fellow Americans. Many of us have lived without power under brutal conditions for extended periods, and as a result are well prepared to do so indefinitely. Many of us have served in the military spending weeks, months or more deployed in the field under brutal conditions as well with no access to heat, power, or even a decent meal. It is not that hard, and it doesn't take long to simply adapt and be comfortable with it.