doomer

I explained it already, I'll explain it again. You can read about this stuff, you know. You can also just ask yourself why the US would spend the money and the time to deploy nuclear capabilities encircling Russia and China when they could save the money and just do it from Kansas and Texas with same effect.

1. To overwhelm missile defenses, you need a large number of missiles flying at each target and you need a large number of targets. This means that the more nukes you have, the better. However, it also means that the more locations your nukes are in the better, because it means your opponent must target ALL of your locations, not just a few. By having nukes in more locations than Russia and China does, the USA begins to undermine MAD because it creates an asymetry. But this doesn't cover why closeness matters, only why distribution matters.

2. To reduce reaction time, you need shorter flight times and longer periods of ambiguity. The less time your opponent has to react, the less effective their response will be. When the US deploys forward nukes, it creates asymetry again. Yes, everyone can load a nuke on a submarine and deploy the submarine, but their capacity is limited. Land-based nukes allow for much higher volume - at least one order of magnitude higher. The asymetry emerges such that when the US chooses to strike first it will give its opponents only about 5 minutes to react before the first missile hits, whereas should Russia choose to strike first the US would have nearly half an hour to react. This reaction time is critical to successful enactment of the MAD doctrine.

There are other points, but let me pause here to combine these two. With high volume, high distribution, and low response time, the USA already undermines MAD substantially. It creates the conditions for a nuclear first-strike where the US is guaranteed to destroy a substantial portion of the retaliatory capabilities of its opponents, which means that mutual destruction becomes less assured. When mutual destruction becomes less assured, you get US military strategists considering how else they can push the envelope to undermine MAD and "win a nuclear war".

Also remember that a retaliatory launch of nukes under the MAD doctrine is not as simple as just saying it. First, the targets of the first-strike have to detect that a nuke is inbound. This is a matter of analysis. It's not like nukes have radar signatures or transponders that identify their payload. Time is critical to determine whether or not nukes are heading your way so you can enact MAD.

Because of this particular problem, most nuclear countries have automatic launch capabilities that trigger when they detect nuclear explosions. This system is a fail safe to ensure MAD. It doesn't work if the first-strike is dense enough and fast enough to take out all nuclear facilities in the first round.

This is the first major step in undermining MAD - high volume, fast delivery speed, globally distributed = able to overwhelm defenses and disable retaliation in a first-strike.

The second major step in undermining MAD is missile defense. This is, again, why proximity matters.

3. Missile detection facilities. By placing nuclear missile detection capabilities in a circle around targeted nations, the USA is able to detect and track missiles at the earliest possible time, far earlier than their opponents can.

4. Missile defense capabilities. By surrounding their targets with missile defense batteries, the USA is able to track AND destroy missiles on their path to their US targets. After a nuclear first-strike by the US, one that has destroyed a significant portion of the nuclear launch capabilities of their targets, whatever remains to enforce the doctrine of MAD will be smaller in volume, easily tracked, and the US will have nearly 30 minutes to shoot every single one of them down.

And that is how proximity undermines MAD.