#3 HAWX - a paramilitary force invades the US in a conventional attack and fights the entire nation's military to a standstill. Inside the first few missions, they lost more planes tanks and men that that of most nations without consequence. In the end, they launched their attack for reasons of ego apparently as there was no strategic benefit to be had regardless of the course the war might have taken.
#2 Modern Warfare 2 - Russia invades the US and achieves complete strategic surprise thanks to magic. While there is a non zero chance the precise moment of an attack could be unknown, the movement of men and material, especially when such movement represent a huge portion of the nation's military, are watched with interest by the entire international intelligence community. Moreover, precisely because single points of failure are stupid for anything made for the military (military equipment WILL constantly be broken, it is only through incredible feats of engineering that there are enough redundant systems to keep them online and functioning most of the time), being able to sabogate a single system would not destroy the capacity to detect such a movement. There was nothing even REMOTELY plausible about the scenario and any defense I have heard lobbied does nothing to close this gaping flaw.
#1 Army of Two - terrorists hijack an Aircraft Carrier. For those unware, an aircraft carrier is BIG. As in the largest vehicles ever made by man big. As in, so big that they have a crew in the thousands. What's more, the ships are built like a FORTRESS and are accompanied by an entire FLEET - cruisers, destroyers and submarines all exist precisely to defend the ultimate arbiter of gunboat diplomacy. To hijack the ship, one must first move past the air cover in some fashion (no easy feat), close through the picket lines of ships (even harder), and then overpower a crew of thousands. Never in history has an aircraft carrier been captured. Destroyed certainly but never siezed. Even if one had the military might required to sweep away the air cover and sink the support ships, they must STILL contend with thousands of armed men and women knowing that a massive gunfight would be required to sieze any of a dozen rooms. Taking control of the command portion might seem reasonable to some, but this just gives you command over the rudder - the engines are controlled in the bowles of the ship ensuring that any attempt to sieze the ship would require literally fighting through every room, every corridor, every door and every sailor and marine on the boat. Were the ship in danger of being seized, it would simply be scuttled. In short, there is simply no way to hijack the vessel - no scenario of surprise or excuse, no level of individual or even collective idiocy, no amount of military badassery will alter this. A carrier can be destroyed but only the most foolish would ever attempt to sieze such a prize.
One last bit about nuclear weapons. In your average nuclear detonation, it all begins with a carefully crafted set of high explosives detonating. This explosion alone is substantial, often including hundreds of pounds of explosive, but in this case it serves a single purpose - to compress the core. You see, all a conventional high explosive is is a vigorous reaction that rapidly produces gas from a solid. This results in a dramatic increase in pressure that can be applied in a destructive fashion. Hand grenades for example simply use this expanding gas to burst the metal shell into high velocity fragments. In most circumstances, producing a very dense material from a less dense material is hardly worthy of notice, but in some cases the effect can be interesting to say the least.
The heart of a nuclear weapon is simply a radioactive metal - either plutonium or uranium. Radioactivity, for those who are unware, is the result of an unstable atomic configuration. In the case of the metals in question, this is the result of exessive neutrons in the nucleus. From time to time a neutron escapes with enormous energy, enough that colliding with another atom can actually destroy the original atom. This is precisely why one gets cancer from radiation - high speed particles are simply punching holes in your genetic structure.
The trouble is, even in a very dense metal, you'll find mostly empty space. In normal circumstances, these neutrons escae and rarely hit anything on the way out. Thus we have a problem - a material that is decaying in a fashion that is releasing tremendous energy but it isn't doing it quickly enough to be useful for much of anything. It was found during the manhattan project that simply stacking a LOT of this material together increased the rate of reaction - a good start but simply increasing wasn't enough - it needed a kick in the pants.
This problem is solved when we make the core incredibly dense - suddenly those escaping neutrons are almost certain to hit something on the way out. When they do, the target atom splits and releases even more neutrons and the cycle continues building power at a frightening rate. When you consider that this is taking place at the speed of light across an object compressed to a tiny fraction of it's original size, you realize that the span of time we are dealing with is fantastically short.
The thing is, natively this reaction is producing kinetic energy in the form of high speed neutrons, electrons are being flung asunder, and a highly energetic particle (gamma particle) is produced in abundance. When a gamma particle hits matter, it loses energy creating light particles (a LOT of them), when those hit something they degrade further into the infra red (heat). Thus if there is matter about, suddenly you have produced a tremendous amout of heat - quite simply kinetic energy. This heat results in a massive expansion of air which results in the actual "blast". Intense heat, high energy particles that never hit anything before hand, and this blast are the cause of the initial damage in a blast. The fact that you just mingled a few pounds of highly radioactive material in with the surrounding landscape and threw it a few hundred miles into the air produces the most notable side effect - radioactive fallout.
This leads to the question - what happens when something like a nuclear bomb explodes in space? Without matter to get in the way, the result is nothing more than a LOT of high energy particles being thrown across the universe. Eventually, with no matter in the way, some portion would hit the ISS and the previously described process still holds true. Particles hit something, energy changes forms and eventually becomes kinetic and damage is done. Without anything appreciably stopping the blast, one can roughly model the damage by realizing that the total energy of the blast is known (the yield), and if one knows the distance from the blast and the area of the station, we also know precisely how much energy the station is expected to absorb. Thus, depending upon the yield and the distance, we could make a fairly accurate guess as to the ultimate fate of the ISS. Sadly, neither piece of information is explicitly given so an accurate accounting is not possible.
To the subject of the EMP - this one is a bit trickier. Electic Fields are the result of particular configurations of electic charge. Placing a conductor in an Electic Field will cause electrons to move about in what you would normally consider "current". Thus any time one begins altering the electrical configuration of a large chunk of atoms a field is generated. The thing is - atoms inherently want to be electrically neutral. In all cases excluding noble gasses however, some portion of the electrons are essentially "on loan" and move about freely. If left to their own devices a while a single atom might be electrically unstable, across a medium it will remain electrically neutral. This is where those high energy particles start ruining lives again - and essentially the result aside from head and light is a LOT of electrons flung asunder creating a very powerful electric field. The stimulus retreats rapidly of course so while intense, it is also quite brief.
Electric fields are quite easy to generate at smaller levels. Simply rubbing one object against another is sufficient to do the job. Even traditional explosions create an EF of their own - just much, much smaller. EMP is thus not a part of *most* nuclear detonations but rather *all* nuclear detonations - assuming of course the particles come into contact with matter.
The trouble is, it is fantastically hard to shield against EF. It can be done, but often the engineering steps required to make it happen are incompatible with the resulting product. Most modern military equipment is shielded from such things to an extent, but there is always a strength of EF that can overcome ANY shielding and result in catastrophic voltage fluctuations.
