[citation][nom]palladin9479[/nom]Umm no, that's not how they work. First rule of nuclear warfare, The TV / Movies are ALWAYS WRONG. They like to create dramatic effects that are wholly unrealistic, usually because the script writers have no idea how nukes actually work.The primary source of damage from a nuke is the pressure wave created shortly after the blast. The flash and gamma radiation are dramatic but ultimately don't do much damage. The power from a nuke must obey the inverse square law, the further from the blast origin the weaker the effect by a power of 2. The power from a nuke is radiated equally in all directions, you can treat it as a perfect sphere. The most of the upper hemisphere (45~48% of blast power) goes up into the atmosphere and only poses a threat to the local avian population. The lower hemisphere (again 45~48%) goes into digging a big crater in the ground (ground burst) or flattening things directly under the blast (low air burst). Your left with 5~10% of the power being radiated outward to do destruction to things outside the fireball (100~800m depending on size of nuke). Due to all these things small tactical nukes are more efficient then large multi-megaton nukes. The most common ones are 50~100kt with 1mt being incredibly rare. Also you tend to target "things" with nukes not cities. You target runways (airport builds are easy to replace with temporary ones), rail yards, military bases, bunkers, command compounds, power plants, telecommunications facilities and such. You hit these things to remove their capability from the enemy and to reduce / remove their ability to respond.Now for actual effectiveness, Hiroshima / Nagisaki experienced large loss's due to the Japanese using bambo and straw as their primary building materials for housing. Those materials provide nearly no protection against the light / gamma radiation or the pressure wave that follows. Today's primary building material inside city's is concrete, something that is very good at deflecting and channeling that pressure wave and is completely impervious to the light / gamma radiation. Targeting a nuke into the middle of a city would just make a really big fireworks display and terrorize the population. Actual damage itself would be limited though everyone in that city would probably have serious psychological issues from such an attack so close. Wooden houses on the other hand are quite vulnerable to the blast wave and would be knocked down unless they were far from the blast center.[/citation]
I don't have time to elaborate on the topic as I'm at work now but you're quite wrong here.
First of all, large cities and population centres are as valid targets for strategic weapons (ICBMs) as other (military) infrastructure. Just read a little about cold war era nuclear doctrines of USSR and USA.
Secondly, ICBMs targeted at population centres do not fall to the ground and explode like bombs - they get detonated (or to be more precise - the multiple nuclear warheads they carry) at some altitude so that the blast and radiation waves have higher spread and are way more devastating than from a simple bomb drop.
As far as effectiveness goes - do not forget that Hiroshima/Nagasaki were quite primitive nuclear bombs. Modern nuclear weapons (strategic ones) use thermonuclear warheads which are more devastating.
Basically, if you don't get killed in the blast (heat) wave or the initial radiation burst you will die within days or weeks mostly due to radioactive fallout which will cover large areas around the main explosion centre. This is especially true in urban areas where the irradiated dust/debris from destroyed buildings will be thrown up high in the air.