Never mind the clutter of the example above. The important thing to remember -- that for each phase of a missile's ballistic flight it require an increasing technical, financial, political, and militarily capable country to reach that phase.
And...Whenever I see someone bring in MARV, MIRV, and assorted acronyms, I know the person is just trying to hide his ignorance behind the alphabets.
Let me guess: you are going to charge me with not knowing what MaRVs or MIRVs are?
Anyway...The sooner into a missile's flight that you want to effect an interception, and that is the desirable goal, the closer you must get to the launch point. The closer you want to get to launch point, the more capable your military must be. You cannot have such a capable military unless you have a sufficiently strong economy to support that military.
Terminal stage is not "soon" into the missile's flight phase.
To date, the only country that can station itself near a potential adversary's ICBM launch point -- and please do not bring in multiple launch points as this is only a simplified example -- is the US. We can station a very strong threat/deterrence like an aircraft carrier group off the coast of any country in the world. Believe it or not, we can launch an air attack, from verbal order to catapult action, quicker and faster than the same can be said for an ICBM launch.
Good luck in trying to pinpoint JDAMs onto a SSBN or seeking out launch sites hidden in caves or mountains. Oh, and don't forget that some ICBM launch sites have fake missile silos.
That's, of course, assuming that the enemy does not possess anti ship ballistic missiles (*cough *cough Iran?).
If a country cannot have that kind of global reach, then the next best thing is to intercept a missile at the mid-course segment. Financially speaking, very few country can reach this phase. Not only does it require an orbital vehicle, the mid-course segment require long term sensors and this pretty much mean satellites. Another high finance factor that prevent most country from achieving mid-course ICBM defense.
Did I say otherwise? That was what I was trying to get at.
You can pay for a few high altitude systems, or you can risk losing entire cities to ICBMs. The choice is yours.
Finally...The last line of defense is the 'terminal' segment. This is where the enemy's weapon is closest to home soil and is most uncomfortable for all. But this is also the most financially affordable defense segment for ALL countries. It does not matter if the defense is bought or indigenously developed. As long as the 'terminal' segment defense is capable enough and can be fielded, it is affordable.
Yeah, with a huge decrease in launch window and kill probability.
The 'terminal' segment defense does not require the country to station itself off the enemy's borders, land or sea. It only require the country to be vigilant, as in very capable sensors looking up as high and as far towards the horizon as possible. This is also much more financially affordable than having orbital satellites, EM monitoring stations, aircraft carrier battle groups, and/or repeated aerial reconnaissance near the enemy's borders.
And it is also much riskier than other systems. Unless you have multiple missiles launching at the same time, it's pretty much a one shot deal.
So realistically speaking...Since not all countries can afford the defense segments like the US -- not even China or Russia -- what constitute an effective and enviable ICBM defense should be the 'terminal' segment. If the country cannot afford rotating aircraft carrier battle groups to deter an enemy by being off his coast, then the financial of one aircraft carrier battle group should be allocated towards the 'terminal' segment defense and make that defense as high an altitude as possible.
Or the midcourse segment. Both are missiles and both don't require aircraft carriers on patrol. One is simply a larger and more sophisticated missile, and even though more expensive, is much more effective.
It's also a fact that missiles have the lowest velocity when in their midcourse stage, and they do not suddenly change trajectories or velocities, even when MaRVs are equipped, which makes it the best stage for interception.
If the country can afford two or three aircraft carrier battle groups, then a choice exist: Either field a rotating deterrence off the enemy's coast. Or expand that ICBM defense into the mid-course defense segment. If the country is wealthy like the US, then allocate resources towards all segments.
This is why criticizing that 15km interception altitude is being simple minded. Even for US, we do not take that capability lightly and we are financially capable enough to be working on all three segments. Any country that is technologically sophisticated and financially capable enough to develop a terminal segment defense that is kms over home soil is one to be respected. We do so respected.
Of course, there's different layers of defense and every layer counts. I've never said I didn't respect the Indian engineers who put hard work in the Akash missile system. But arguing somehow that 15 km interception is somehow more than or just as effective as midcourse interception is ridiculous.
