If another nuclear bomb is ever exploded on a city, what is the most likely scenario?

Meh, we got more than one nuke.

A few papers on, from people who presumably know what they are talking about, on Pakistani nuclear weapons issues, including command and control:
NTI’s profile on Pakistan’s nuclear forces, including history and C2;
Challenges for Pakistan’s Nuclear Security, published by the Arms Control Association in 2013;
and a paper I’ve linked here before, from the South Asian Strategic Stability Institute in 2008, Pakistan’s Nuclear Command and Control: Perception Matters. All of them have additional cites for further research.

Basically, the gist I got from reading these is that Pakistan has increased the scope of its security efforts, including utilizing PAL-like device security precautions, increasing the effort put into their PRP-like programs, and, more importantly, not publicly accepting U.S. help with the first two areas. The thought is that the U.S. would use such access to deactivate Pakistan’s nuclear deterrent. However, the 2012 attack by Tehrik-e-Taliban militants on the Minras/Kamra Air Base, which resulted in the wounding of the base commander and loss of a jet, has not completely reassured outside observers that Pakistani nuclear devices are adequately protected from theft or sabotage, and if stolen, are not immune from unauthorized use. It’s a problem that has afflicted the U.S. too—google the RAF raid on the U.S. Army depot at Giessen, West Germany in 1977, where the RAF tried to steal nuclear demolition munitions—and probably the Soviets/Russians too. Modern PAL-type devices should inert the munition on attempted unauthorized access, and hopefully the Pakistani armed forces have similar devices/construction designs for their munitions.

My own twist on the OP is that we know that radiochemistry is good enough to identify the source of nuclear material, and we know that weaponized fissionable nuclear material may have been lost/misplaced/unaccounted for by both the ex-Soviets and the U.S. My question is, can a non-state actor’s fission (or multi-stage, if we really want to freak out) device that used, say, the old HEU stocks from the Soviet nuclear submarine fuel, that was famously bought by the U.S. in operations like Project Sapphire, be distinguishable from a device constructed by the Soviets from that same fuel source? IOW, could we tell between a device stolen from a state actor, and a device made by someone else from fuel stolen from that state actor? How about if most of the components between the two devices were identical, like the tritium used for injection, the neutron generators, the case material, and fuzing equipment?

If we really can’t, if I were in a decision-making position in one of the nuclear states, I’d be having a lot of sleepless nights worrying that some fanatic could use our fuel to blow up, e.g., Washington D.C., and we’d get blamed for it.

I doubt Israel has any nuclear weapons. They don’t need them. Now if a country like Iran builds some, then that will change. Iran is just asking to get itself and its wonderful history obliterated.

India and Pakistan, with Pakistan beginning the festivities and India ending them.

It is one thing for random Islamic nutjobs to want to acquire nuclear weapons, and quite another for members of the army, navy and the air force to be radicalized and carried away in jihadi fervor. The Pakistani forces - particularly the army and AF - are heavily radicalized and deeply penetrated by Taliban and AlQ. The AF officers facilitated penetration of PAF Mehran by Taliban gunners during the attack on that base.

Quite apart from the fact that Pakistan has enormous challenges with the Taliban and AlQ, who all wouldn’t mind a few additional kilotons in their arsenal, Pakistan displays systemic irrationality, with politicians and generals and roadside tea sellers all promising to crush India for whatever reason. It’s a Pakistani national pastime. Ex-ISI creep Hamid Gul famously threatened to nuke Bangalore for some goddamn reason.

You do not need an AF or missile to deliver nukes in the India-Pakistan context. The long and porous border makes it viable for jihadis to smuggle in components and assemble them later for detonation, offering Pakistan “plausible deniability”.

India’s stated policy is massive retaliation, so the escalation chain would be rapid and uncontrollable. Needless to say the human cost would be horrific.

They’ve got 'em. Why wouldn’t they? And unlike rogue states, the UN hasn’t sent any inspectors to Israel because they’re America’s puppet. Everyone knows that.

Regarding all-out nuclear war, it’s unlikely to ever happen, except perhaps for India/Pakistan in the rather distant future. It’s scary to even think about a nuclear terrorism scenario, but were we to be so morbid as to make predictions, I’d guess some place in Russia by Chechen terrorists (or even al-Qaeda) stolen from the former USSR arsenal.

Anyone ever inexplicably lost power (no wind or storms, bills all paid) and your first thought is to look outside and see if all the cars on the streets have stopped?

Not since 1991 or so. Before then, yeah sometimes.

Yes, hoping it’s flying saucer related.

I don’t think Israel has nuclear weapons because they don’t need them and it would be unpleasant for their presence to become known somehow. It doesn’t do to make assertions of which one has no proof beyond ideology.

Israel has the infrastructure to produce them on a dime. The reason Israel hasn’t been inspected is that Israel has not allowed it. There are many reasons for this, including the hassle and the fact that a negative result would not be believed anyway.

By the way, referring to Israel as America’s “puppet” is kinda a giveaway that your thinking here is not very clear and ideological rather than rational. Israel does a lot of things the Americans (especially the present administration) don’t like.

Or maybe it’s because they’re not a rogue state.

[sorry, folks, but I just wanted to respond to one comment. Let’s all agree not to hijack this thread into yet another trainwreck of Israel bashing.]

As far as I am concerned in one way or another almost every country on the planet is a “rogue” state. However most people limit it to North Korea and maybe Byelorussia and Zimbabwe. Russian behavior of late has not been so sterile either.

This. Either the India/Pakistan will go over the brink, or the NK regime will collapse and lash out in some final “screw you” gesture at the world. Probably at Japan if they can reach it; they have conventional artillery to devastate SK.

Mordechai Vanunu seemed to think that Israel had nuclear weapons in 1986. If you have a subscription to the Sunday Times, you can even read the 1986 article that got him into so much trouble. I tend to believe him, FWIW, mainly because of the Li-6 work he mentioned. There are other countries thought to be in the “we don’t have nukes, but we can make them by tomorrow” club—Japan, Taiwan—but I don’t think Israel’s one of them.

Was it ever confirmed that the Israelis were seriously contemplating tactical nuclear strikes during the Yom Kippur War?

Israel says it doesn’t have them, and it has no reason to have them and a lot of reasons to not have them, as I already pointed out. There is also no evidence it has them. The rest is propaganda.

Hello? 1986 is calling.

What about the Vela Incident?

And how can you possibly claim that Israel has “no reason” to possess nukes? They’re surrounded on all four sides by hostile, aggressive neighbors who hate them with a passion AND perceive Israel’s existence as thoroughly illegitimate. Already, Israel has been invaded twice by an Arab coalition (and fought 'em off, good on them) so WHY hasn’t the Middle East descended upon them again?

Not only that, if the Middle East does indeed someday erupt into a Hot War, Israel could nuke its neighbors and merely say, “My bad!” while the USA and the rest of their allies could say, “Tsk-tsk, hey it wasn’t us.” (That’s the whole point of a superpower owning puppet states, by the way.)

I think Israel doesn’t have and doesn’t want to have nuclear weapons; this would hand all their hostile neighbors reason to build their own. Also, if Israel has them, at some point it would come out to everyone’s embarrassment.

It is not true that Israel is surrounded by enemies. Most of the countries thereabouts would like to see Israel go away but are long resolved to their presence and a few even prosper from it. Others cooperate in all sorts of unstated and tacit ways with Israel.

The Iranians are really stupid if they end up with a nuclear arsenal, because that will force Israel to act and the Iranians will come out destroyed. Israel has the time needed and need not act until really quite a bit later. I think the Iranians will play this card as much as they can to get things they want, but I hope and pray they are not that stupid. Iran is a great country with a heritage the world would very much not want to see destroyed.

The Iranians keep one eye on Israel and one on Saudi Arabia. Iran’s security calculus is more complicated due to the Shia-Sunni schism, and the hostile geopolitics that flows from it. SA has strong US support and a vassal state armed with nukes (Pakistan) that is also willing to sell them for a dime and some oil. Iran really should get nukes - that will checkmate the Saudis and the influence of Wahhabi Islam, currently the engine of Islamofascism.

Anyway all this is OT, so no more from me.

The Saudis do present something of a problem for Iran, but not enough of a problem to cause them to need nuclear weapons. What do you envision, a Saudi invasion? The Wahhabi bit is really old propaganda; the stuff was current maybe in the 1920s and never was more than maybe ten percent.

I’m going to bed so I guess someone else will get the last word.

I have no idea what the Vela Incident actually was. I tend to think it was a piece of space junk/meteoroid that triggered the double-flash warning from the Vela, given the U.S. flew multiple snooper flights through the area, yet (officially) didn’t find any evidence of a nuclear test. The ‘gun-type’ uranium-fission weapons developed by South Africa shouldn’t have needed any testing with HEU. Little Boy, after all, was of a similar type, and thought to be idiot-proof enough to not require a full scale test before using it against Hiroshima. Moreover, evidence including the interval between flashes, gave the yield of the “explosion” at around 2-3 kilotons, much smaller than the 12 kt of Little Boy. Perhaps, if it was a joint South African/Israeli test, it was a test of a miniaturized gun-type or implosion type fission device, a device that would more efficiently use the limited amount of fissionable material available, but required testing to prove it worked?

OTOH, South Africa was thinking about also developing thermonuclear devices, which also require the use of a fission explosion. The advantage with a multi-stage device is that, besides being able to be scaled much larger than a pure fission explosion, they utilize less scarce ingredients than purified plutonium-239 or uranium-235. They are much more challenging to make, however. Perhaps the test was to determine whether the fission primary in a putative thermonuclear weapon would have the output needed to trigger fusion? Maybe it was a proof-of-concept for weapons to be sold by Israel to South Africa? I find the idea that a nuclear state would sell weapons to another state (that presumably couldn’t make them itself) absolutely mind-boggling, and wouldn’t be surprised if those documents actually were propaganda.

Anyway, though this will no doubt be dismissed as yet more propaganda, the historian Avner Cohen has made public an interview he had with Arnan Azaryahu, an aide and senior adviser to Yisrael Galili, wherein Mr. Azaryahu talked about an October 7, 1973 (the 2nd day of the Yom Kippur War) meeting with Moshe Dayan and Golda Meir concerning whether Israel should use some of its nuclear deterrent as a “demonstration.” Dayan was for it, Meir against it, and the matter was dropped. Per Mr. Cohen, this “is the first and only testimony made by a credible, identifiable source regarding a discussion of the nuclear issue at the level of the Israeli war cabinet.” An New York Times op-ed written by Mr. Cohen, placing the interview into context with other journalists’ articles about Israel’s actions concerning their nuclear deterrent in October 1973, may be found re-printed here. It’s where I found the above quote. I found them interesting to read, especially the Seymour Hersh-bashing that most foreign affairs commentary seems to love indulging in.

Other evidence that the Negev Nuclear Research Center (AKA “Dimona”, after the town 13 kilometers away) has been involved in a bit more than research is just its sheer size. For comparison, the most powerful academic research reactor in the U.S. is the University of Missouri’s Reactor Research Center, at 10 MW thermal output. The IAEA lists Dimona as having a thermal output of 26 MW, but outside observers, taking into account additional building expansion and other evidence, list Dimona’s output in the 70-150 MW range. The article, Should Israel Close Dimona? The Radiological Consequences of a Military Strike on Israel’s Plutonium-Production Reactor, in the May 2008 issue of Arms Control Today, mentions other research reactors in the area, (i.e., not used to also produce electric power), like

And finally, here’s a 1999 paper in the USAF’s Counterproliferation Papers series, The Third Temple’s Holy Of Holies: Israel’s Nuclear Weapons, “a history of the Israeli nuclear weapons program drawn from a review of unclassified sources.” I found it short, lucid, and to the point.

I’ve been unable to find a definitive answer, but would the U.S., due to prior Acts of Congress, legally be allowed to continue to supply aid to Israel if Israel were to overtly claim that they had nuclear weapons? If so, that could be one reason why Israel and the U.S. have always been coy about whether Israel has them or not.