It’s probably a good idea to read my earlier post on why nations don’t want nuclear weapons before reading this one. The various factors in a decision to build a nuclear arsenal weigh differently for the nations that are variously considered to be candidates for that decision. There is no one size that fits all.

The deterrence value of nuclear weapons is not as absolute as much of today’s discussion would have it. Israel has nuclear weapons and yet was attacked by Hamas. India and Pakisan both have nuclear weapons and yet conflict from time to time.

What size nuclear arsenal will deter a larger nation from attacking a smaller one, and how does a nation building a nuclear arsenal avoid being attacked while it is doing it? And then there is the additional requirement of a way to deliver the nuclear weapons to a target. Nuclear weapons are not the whole of a deterrent.

North Korea can easily destroy South Korea’s capital, Seoul, with conventional weapons. As we see, Iran has control over a large fraction of the world’s petrochemical and allied industries through the Strait of Hormuz. Although a nuclear weapons program is expensive, cost may be the least important of the factors.

A determined nation will find the funds. But the cost probably has been part of the considerations for nations that are not strongly motivated. Perhaps most important is that a decision to build nuclear weapons changes the character of a nation.

A clandestine program puts the nation into a relationship of distrust with other nations. Breaching or renouncing the Nuclear Nonproliferation Treaty puts a nation in a category with North Korea. On the other hand, a nuclear weapons program may be an object of national pride.

Let’s look at specific nations. I’ll assume they all have the scientific and technical know-how necessary to build nuclear weapons. Iran.

First, Iran does not have nuclear weapons. No intelligence service has assessed that it has a nuclear weapons program. The International Atomic Energy Agency has found no evidence of a nuclear weapons program.

Iran complied with the JCPOA, the agreement negotiated by the Obama administration, until Donald Trump abrogated the US side. After that, they were explicit about the steps they were taking and stated a desire to return to the JCPOA. Iran is a signatory to the Nuclear Nonproliferation Treaty, which is a certification that they do not intend to build nuclear weapons.

Will the attack by Israel and the US change Iran’s postion? The Trump administration has not understood that Iran’s insistence on maintaining the capability to enrich is a matter of national pride and perceived need. Foreign suppliers of nuclear fuel for Iranian reactors have been unreliable.

The enrichment program is a source of national pride. Iran has used that program as a lever to remove sanctions, but they were compliant with the JCPOA. The deterrent value of the Strait of Hormuz is now clear to the Iranians.

Control of the Strait is much less expensive than a nuclear weapons program. On the other side of the deterrence equation, nuclear Israel has been acting with impunity that Iran might want to counter. The IRGC seems to have gained power, and the advocates of nuclear weapons have been largely in the IRGC.

Iran’s nuclear infrastructure has been badly damaged and will require time to rebuild. That may make it easy for Iran to offer a five-year period in which they limit enrichment. As was the case in 2015, the largest factor will be the agreement to end the war.

If Iran feels secure, nuclear weapons become less attractive. Ukraine is often claimed as the example of a nation that should have retained the Soviet nuclear weapons on its territory. I’ve argued this in more detail.

The big factor in Ukraine’s decision to send those missiles to Russia as Belarus and Kazakhstan did was the effect that keeping them would have had on its future. Europe and the United States wanted those missiles to go back to Russia. They did not want more nations with nuclear weapons and the complications that would bring to international relations.

If Ukraine had insisted on keeping the missiles – and there was an intense debate both with other nations and within Ukraine – its relationship with Europe and the US would be cooler. It might have been necessary to get help from Russia for maintaining the missiles. Ukraine could have wound up closer to Russia if it had kept those missiles.

A number of nations, including Sweden, Switzerland, and Taiwan, have started out to build nuclear weapons programs and ended them before producing a weapon. That judgment is likely to hold for all the negative reasons above. Japan and South Korea see North Korea as a threat.

Japan has a stock of separated plutonium that could be made into weapons. Both nations depend on assurances from the United States of nuclear protection. As Trump makes the US more unreliable, their motivation to build their own nuclear arsenals will increase, but they are currently fa