>> suggesting that the hundreds of weapons the Soviets had pointing at the UK were complete overkill...
As Schlosser says in his book - because of the lack of coordination between the Air Force, Army, US Navy and Missile Forces, at one point there was something like 400(sorry if I remembered the number wrong,but it was in hundreds) nuclear rockets aimed at Moscow, many of them with multi-megaton payload. If they were launched, Moscow wouldn't be just destroyed - the entire area would be turned into the biggest crater on earth.
A point that bears repeating is that this level of overkill was actually counterproductive. One way of disabling a high efficiency nuclear device is to blast the thing with neutrons (causing a premature and incomplete fission reaction in the core of the weapon). This was actually how the Sprint ABM system was intended to destroy its targets:
Now picture the skies over Moscow with ~400 warheads coming in, most of them having been launched in a coordinated wave by Minuteman, Titan, or MX missiles within the space of a few minutes: it turns out that the prompt neutron pulse, blast, EMP, or thermal effects from one incoming warhead can disrupt another if it arrives within 10 seconds of the first. This is termed nuclear fratricide:
One explanation of the massive overkill that the US had for a lot of the Cold War came down, essentially, to badly stated requirements.
Apparently, the US military were tasked with destroying 50% of the socialist world's industrial capacity - which you could do by destroying 50% of the factories completely or 100% of the factories by at least 50%. However, if you attack say a shoe factory (the example given) with an H-bomb aiming to achieve at least 50% destruction you do actually get 100% destruction. So all factories were targeted.
NB I used the phrase "socialist world" as, at least until well into the 60s, the SIOP aimed to destroy everyone even vaguely left of center whether they were actually allies of the Soviets or not (e.g. China, Albania, Yugoslavia etc.).
Pretty sure I read this in "The Bomb - A Life" by Gerard DeGroot, but I could well be wrong!
Maybe, but another important reason for overkill is that you couldn't be sure that all payloads would actually reach their destination. In the nuclear-bomber era this was especially the case - IIRC the last book I read on LeMay suggested that planners assumed around 90% of the planes would be shot down far away from their intended targets. The missile era obliterated that particular dynamic, but replaced it with a threat against second-strike capability from your enemy's ICBMs.
Most of the politics at that time wildly overestimated the capabilities of the Soviets in public (hence the infamous bomber and missile gaps) while internally having pretty accurate and poor estimates of their capabilities - LeMay at one point expected that the SIOP could be implemented with pretty low levels of casualties.
Air defence systems back them were really pretty poor - e.g. the infamous case where the entire US air defence system couldn't stop UK strategic bombers taking out major us cities in an exercise (which was kept quiet for decades due to the embarrassment it caused).
"It appears that two weapons targeted on a silo must arrive at least 10 s apart to avoid fratricidal fireball effects, and less than 1 min or more than 1 h apart to avoid fratricidal nuclear dust cloud effects."
Anyone for Missile Defense with a 50-100Mt Tsar bomba?
A primary reason for the generally larger, and in some cases, insanely large throw-weights of Soviet nuclear missiles was their much less accurate targeting and guidance systems.
If you can land a nuke, or even a conventional warhead, directly on whatever it is you're trying to make a was, your required explosive yield falls dramatically.
Blast radius and damage increases with the cube of yield, so if you're half as accurate, you need 8x the blast, generally, for effective damage.
Turns out that with extremely high precision warhead delivery, the US can dispense with nuclear weapons even for tasks such as destroying deeply buried and reinforced bunkers (command and control, or missile launch).
On the one hand this makes nuclear Armageddon that much less likely. On the other it makes use of highly advanced weaponry less objectionable.
Which way the risk needle ultimately swings given that calculus is an interesting question.
I remember the figure of 400 as well - don't know if that included UK weapons as well (e.g. the Chevaline upgrade to Polaris was mainly about defeating the ABM defenses around Moscow).
NB An interesting article by Charlie Stross on the relationship between the US and the UK's "independent" deterrent:
I don't think anyone knows what would happen to an area after 400 detonations.
My (wild) guess is that you'd get a blob of extremely hot rock melting its way down through the crust and enough fallout to sterilise the Northern hemisphere.
So kind of a dumb idea from a strategic point of view.
It is, but that's the problem - Air Force, Army,Navy and SAC controlled their own missiles and apart from the fact that they would all launch theirs if they got an order from the president, they didn't coordinate when it came to which targets each one of them would hit. So the Air Force might have had a plan to hit 100 points around Moscow, and so did the Army,and so did the Navy,and so did the SAC. So at the moment of launch 400 rockets would be hitting the same spot,because the attack would not be coordinated.
The risks of having an uncoordinated attack were known pretty early on - e.g. having bombers blowing each other up, bombers destroyed by missile attacks etc. That's why there was the SIOP:
As Schlosser says in his book - because of the lack of coordination between the Air Force, Army, US Navy and Missile Forces, at one point there was something like 400(sorry if I remembered the number wrong,but it was in hundreds) nuclear rockets aimed at Moscow, many of them with multi-megaton payload. If they were launched, Moscow wouldn't be just destroyed - the entire area would be turned into the biggest crater on earth.