TL;DR it's important to have the ability to launch nukes even if the President is insane, that's why it goes through a chain of command rather than from POTUS directly to the button pusher. I just have a lot to say, sorry for putting my soapbox here. This starts on topic and goes off the rails at the end.

This is a tough call. I agree with the premise that it's quite important to make sure that an insane president can't launch nukes. At the same time, this is a fundamental issue in the military -- when they say he lacked the qualities of "leadership" what they really meant was "followership", which is a concept not really taught to us in school. Everyone in that organization has a role to play, and if they don't play that role then they are not welcome. This isn't an organization where you join to really be a leader in the "trailblazer" sense, but a leader in the "set a good a example by demonstrating how to follow the rules properly" sense.

Does that mean an officer in the military is absolved from making moral choices? Of course not. They have the free will to say no, to not do what they're told, and to abandon their role. Of course there are consequences for that, but that's not really the issue. Doing the right thing isn't supposed to be easy and consequence free. In fact it's usually quite the opposite, which is why courage is a virtue. But the point is the choice to not press the button always exists.

Also, it's worth pointing out that truly insane people are not subtle about it. I don't know how many people here have talked to genuinely insane people. but from my experience they can't go very long without revealing they are abjectly and certifiably crazy. Someone in that state of mind would have been acting crazy for quite a while (it takes time to go from a sound mind to "NUKE THE WORLD"), and everyone around him would be keenly aware of his behavior. It's destructive by its nature, and does not go around quietly.

Diseases of the mind are quite loud and they are also infectious, if people aren't aware. Not that I mean you can become literally insane in the presence of insanity, but that insanity ramps up your anxiousness, because of how unpredictable and... well insane they are behaving, which in turn degrades your decision making capabilities -- "Well, I could do this completely sane and rational thing, but that would upset the insane person I'm with for illogical reasons. But I'd rather not upset them because that's upsetting to me, therefore I will act irrationally and that's somehow the most rational thing to do". See how twisted it gets? That kind of logic is unsustainable for a rational mind for long, so if you're forced to endure those mental gymnastics, all critical thinking shuts down and you just become a reactive nervous mess. Insane people leave a wake of chaos behind them at all turns. It's not subtle.

Notably General Mark Milley recognized this in Trump at the end of 2020, and assured his chain of command that any nuclear strike order would be issued from the President to Gen. Milley and then he would transfer that order down the chain. What Milley meant to convey with this statement was that any order for a nuke would be lawful, because he would only have advanced it if he deemed it lawful. Not the President. Right, because who determines whether a strike is lawful? Not a court. Not the congress. Maybe after the fact they would have a role but not in the heat of things. The President can issue a strike but his issuance does not make it necessarily lawful; nuking California because they voted against you in an election for example would be an unlawful order on its face. So really the lawfulness of a nuclear strike order is determined in situ by the individual members of the armed services as they pass the order down the chain of command. An unlawful order can still make its way through the chain under these circumstances, but at least it's something. Because what's the alternative? Anything else would slow the process down to a point where the nukes would be completely useless as a deterrent; you have to have the ability to launch them in a timely matter. Because if your opponent knows it takes you 3 months to get an authorization to launch a nuke while you wait on the result of the President's mental health assessment and subsequent lawsuit and court appeals, then MAD completely breaks down.

The President doesn't go directly to the button pusher with an order to push the button. There are channels and even if there isn't apparently a "two man" rule for nuclear strikes, it still originates at the President and goes through a number of personnel. Any one of them has the agency to say no and refuse the order as unlawful. Now, the further down the chain you go, the less weight a refusal carries. That's because each link in the chain acts as a sort of authentication, so you don't have to trust the President is sane, you just have to trust that your direct superior is sane. What Mark Milley was telegraphing at the end of 2020, was that he himself was in fact sane, and any order subordinates might receive would have be effectively laundered by his sanity, even if the President were insane.

And come to think of it, how would that play out?

Insane President: Launch the Nukes
JCS: No.
Insane President: Okay then I will fire you.
JCS: No you wont.
Insane President: And why is that, I have absolute authority.
JCS: If you do then we're going to tell everyone that you fired us because we refused to carry out your nuke order. And then we will reveal that we had been planning a preemptive nuke, which will cause our enemy to preemptively nuke us.
Insane President: Well why would you do that?! You would be nuked too!
JCS: You're right that would be bad. So then don't fire us.
Insane President: But then how would I nuke them?
JCS: .... you don't....

Right? How would the nuke order go anywhere if the JCS doesn't endorse it. So in that sense there is a kind of two man rule but it's at the top end.

Because what if the President were insane but we also really needed to launch a nuclear missile for a good reason. Well that might need to happen immediately and we can't have random people in the chain of command refusing orders because they have some negative perception about someone far removed from them in the chain. That opens up a whole other world of problems.

So that's why I think an insane President is not likely to be able to launch a Nuke.

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Now, the issue is a little bit different in Russia. Putin is not insane, he's a narcissistic psychopath -- the worst kind of psychopath. He has been on a huge power trip the last 6 years, and his ego has been inflated to the size of the universe. What's happened in Ukraine has popped his bloated head. It's caused him the gravest narcissistic injury, which I won't describe here, but I'll leave it to the professionals: https://medium.com/@Elamika/hell-hath-no-fury-like-a-narciss...

Narcissistic rage is one of the darkest and deadliest forces known to mankind. Before it erupts, it usually simmers and percolates for a long time, fueled by resentment, envy and entitlement, the latter always aggrieved as the narcissist’s need for adulation and glory is insatiable and he can see the world populated by the undeserving, inferior people who nevertheless dare to be happier and/or more successful than he is. It thus creates enemies out of the innocent and often weak who become vessels for the narcissist’s hateful and envious projections.

This article is written with respect to Trump, but Putin and Trump are both narcissistic psychopaths of the highest order so it applies to both of them equally (and no one has to wonder anymore why just last week Trump was calling Putin a savvy genius for what he's doing in Ukraine). But Putin being a narcissistic psychopath means that he absolutely can and will give the order to launch a nuke, and I don't enough about the Russian system to say anything more. Other than the fact that Putin's character disorder means that this conflict ends in 1 of three ways:

1. Putin kills himself Hitler style (also a narcissistic psychopath), as his war effort and country crumble around him.

2. Putin's citizens find him and string him up at the gas station Mussolini (ditto) style, or they find him in a hole in the ground Saddam style (yet another one, seeing pattern?).

3. Putin is murdered or deposed by his generals as he goes off the deep end.

That's it. This is going to keep on going until Putin is gone. Everyone trying to offer him an "exit ramp" or trying to give him an "out" so he can "save face" just does not understand the interplay between Putin's narcissism and his inability to let this go. Narcissistic rage doesn't go away because the target of your rage assuaged you. That is just your target signaling their weakness and vulnerability, and really giving you permission to strike. That's the mind Putin has. There are a lot of "pundits" right now who are out on the internet completely perplexed as to Putin's motives. They say "He can't hold Ukraine, he can't install a puppet government there, what does he want? For the life of me I can't say so he must be inane and completely irrational." I mean, yes and yes he is, but only from our perspective. Within his framework his decisions are completely rational. And his framework is this (it's from the article).

1. I am great.
2. People unfairly malign me.
3. I will show them (they will pay).

We're at stage 3 right now. "They will pay" doe not go away until they have actually paid in the eyes of the narcissist. You can't give the narcissist a "way out" because they don't want out. Their motive is nothing beyond revenge. It's not like Putin bit off more than he can chew and he's desperately looking for a way to get out. No, he bit off more than he can chew, but he wants to shove it down his throat and choke on it because at least maybe he would get his revenge in doing so. He's willing to sacrifice all of Russia or even the entire world for this revenge, and I think people are still unwilling to fathom that. He wants to kill Ukrainians. He wants mass murder on purpose. The phrase "If I'm going down I'm taking you with me" comes to mind.