Pretty much. Current ABM systems are (at best) in the order of 90% effective, so assigning ~10 warheads to your target gives you a good chance that one will get through. Russia is estimated to have approximately 4,300 warheads; So the question for anyone relying on ABM defense in a war with Russia is: Which 430 cities don't you need?
- - - Updated - - -
Therein lies an interesting question. If everyone had nukes would our modern concepts of war become obsolete?
Yes. Just as everyone having chemical weapons made war obsolete after 1918.
Oh, wait.
Shit.
I think there's several orders of magnitude in difference between the two. Chemical weapons merely make war more miserable and terrible than it already was. Hardly a reason to stop if the rewards are good enough.
What reward is worth facing nuclear annihilation?
It was anticipated by both the British and Germans that chemical warfare against civilians would be used in WWII; Both sides had used it quite liberally against each other's military positions on the Western Front two decades earlier, and feared that its use against their cities would be devastating. Blister agents, such as mustard gas, would have been particularly difficult to defend against - the universal issuing of gas masks to the civilian population would have done little to protect against agents that can be absorbed through the skin, and are highly persistent. The results would have been devastating, and both sides knew it; As a result, neither side was prepared to be the first to use these weapons, lest they be subjected to retaliation in kind.
Of course, at the time, nuclear weapons didn't exist; These chemical weapons were the most frightening weapons of mass destruction that were available. Even Hitler resiled from their use - and given his readiness to use similar weapons against people who could not fight back, we can only assume that this was for fear of a retaliatory strike. Yet all of the horrors of war short of chemical weapons were unleashed by both sides, without apparent fear that a conventional attack might lead to a breakdown of deterrence with regard to chemical weapons.
The effectiveness of a nuclear deterrent rests on the understanding on both sides that the other side are willing to escalate to their use. The Soviets had good reason to believe that NATO would not hesitate from first use of nuclear weapons, in the event of a large scale conventional conflict in Europe; It was obviously less clear how NATO might respond to smaller scale conflicts, and such conflicts were commonplace during the Cold War, particularly outside the European theatre. The American (or Russian) people would not tolerate their leaders risking the very existence of their nations over some squabble in Africa or South East Asia, so both sides could act in those regions with little fear of precipitating a nuclear war.
Where no overwhelming justification for their use exists, it is hard to imagine any nation wanting to be the first to escalate to the use of WMD - but that makes these weapons ineffective at deterring conventional warfare.
Nuclear weapons also "merely make war more miserable and terrible than it already was" - unless you use a lot of them, and annihilate your opponent. If you believe that your ABM shield provides adequate defence to push the consequences from 'annihilation' to merely 'miserable and terrible', then why not go to war?
People may, perhaps, have less stomach for it today, but even before the nuclear age, the almost total loss of a city (or two, or three, or a dozen) was not sufficient to defeat anyone. Coventry, Hamburg, Dresden, Tokyo; All were destroyed just as completely as Hiroshima - the difference was that it took a bit longer, and a lot more aircraft and munitions, before the A-bomb became available.
