Here's a sobering quote I read at Ars technica. All too realistic for those of us who lived during the duck-and-cover era.
I'm sure the US military must have the efficiency of using their warheads for maximum devastation all worked out.
A Chinese Officer here once on exchange (billed as a "look what we can do" session it was really a "look what we can do to you" exercise) produced the standard line about how the Chinese could lose 500 million people in a nuclear war and keep going with the survivors. So his hosts got out a demographic map (one that shows population densities rather than topographical data) and got to work with pie-cutters using a few classified tricks - and got virtually the entire population of China using only a small proportion of the US arsenal. The guest stared at the map for a couple of minutes then went and tossed his cookies into the toilet bowl. The only people who mouth off about using nuclear weapons and threaten others with them are those that do not have keys hanging around their necks. The moment they get keys and realize what they've let themselves in for, they get to be very quiet and very cautious indeed. Another great - and very recent example - look how circumspect the Indians and Pakistani Governments were in the recent confrontation - lots of words but little or no action to back them and both sides worked very hard not to do anything that could be misunderstood. (When the Pakistani's did a missile test they actually invited the Indians over to watch in order to ensure there was no ground for misunderstanding. The test itself was another message from both countries to the rest of the world - basically it read "Don't sweat it, we know the rules")
I'm sure the US military must have the efficiency of using their warheads for maximum devastation all worked out.