If the reports about several hundred new missile silos in China are credible, what is driving China to expand its nuclear capabilities?  Is China seriously trying to dramatically expand its nuclear arsenal? 

Different parts of China's modernization program are driven by different factors. The silos are for China's very long-range missiles: intercontinental ballistic missiles that could potentially reach the United States. I suspect that improvements in China's long-range missile forces are about enhancing the survivability of its nuclear arsenal and, in particular, its second-strike capability. China worries that in a conflict the United States might attack its nuclear arsenal preemptively and then use U.S. ballistic missile defenses to mop up whatever surviving weapon China fires in retaliation. Many of the developments in China's long-range nuclear arsenal are about denying the United States the ability to destroy that arsenal. I suspect that there's also a degree of perceived prestige in this as well and a general sense that more nukes bring more security. For the most part, however, this expansion is about the survivability of Chinese forces.  

That said, this is not true of all of China's modernization efforts. The Chinese are also developing and increasing the number of some shorter-range missiles that are dual-use. This means that they can hold nuclear or conventional warheads. The DF-26, an intermediate range missile that can have a nuclear or conventional warhead, is an example of this. The development of these missiles is not about the survivability of China's arsenal, but instead about creating new options for limited nuclear use in a conflict.  

We can't look into the minds of Chinese leaders and know exactly why they are authorizing this, so there's some degree of uncertainty here. In any case, be careful to distinguish between different developments since they serve somewhat different purposes. 

China has long maintained a small nuclear arsenal and preserved a strategy of “minimum deterrence.” Based on new developments in China’s growth and modernization of its arsenal, is China shifting its strategy toward nuclear war-fighting?

A lot depends on what you mean by nuclear war-fighting. It's a term that means different things to different people. Some think that nuclear war-fighting means thinking about nuclear weapons like gigantic conventional weapons, or some kind of super-artillery that would be used to win a war with brute force by blowing up enough U.S. aircraft carriers, bases and forces. I don't think that is China's conception at all.  

On the other hand, China is no longer merely looking for a survivable second-strike capability. I mentioned that developments in China's long-range nuclear forces are primarily about ensuring its ability to hit the US with nuclear weapons. China can maintain that ability even in spite of U.S. developments and first-strike and ballistic missile defenses. Strategically, the developments in China's long-range forces are about maintaining what it perceives as a minimum deterrent. As for the developments in China's shorter-range nuclear weapons, and the medium and intermediate range missiles with nuclear warhead capabilities, I don't think that’s just minimum deterrence. 

China’s new DF-41 missiles have a large nuclear warhead-carrying capacity, but there is also a strong possibility that not all of China’s new silos will be filled with missiles. Experts believe that China faces serious constraints in a “breakout” due to its limited capacity to produce plutonium and enriched uranium.  Can you talk about how methods like tracking China’s fissile materials production could augment our understanding of how large China’s nuclear arsenal will actually be, and what the limitations of this approach are? How important is it for other states to determine these more exact numbers when it comes to evaluating China’s nuclear threat? 

The DF-41 can certainly hold more than one warhead, but how many it can hold is unclear. As of a few years ago, the public reporting was that it was tested with two warheads. I am quite suspicious of some of these accounts now that say it can hold six or even ten or twelve. 

In terms of fissile material, there are two different kinds of nuclear materials that you can use to build nuclear warheads: highly enriched uranium and separated plutonium. Importantly, plutonium is needed for modern miniaturized nuclear warheads that can fit on a ballistic missile, and certainly the kind that you'd want to put on a MIRVed ballistic missile, which is a ballistic missile that can hold multiple warheads. While we don't know this for certain, it is a reasonable assumption that China needs plutonium in all of its warheads. That's actually quite helpful because highly enriched uranium production is very, very difficult to track. Centrifuge plants in particular are just modestly-sized industrial buildings. They don't use much electricity, and they don't have big output. It's very hard to detect clandestine centrifuge plants. Even if you know there's a centrifuge plant you don't know whether it's producing anything. It is also very hard to determine whether it's producing low-enriched uranium to fuel power reactors or highly enriched uranium for weapons.  

Plutonium production is much easier to track. The nuclear reactors produce a heat signal; the fuel must be removed from the reactor and processed to extract plutonium. All of this is a fairly big, visible process. We can have a pretty good idea if other states are reprocessing it, and we know China’s dedicated military facilities are clearly all shut down. China has one civil pilot plant known for producing plutonium. Its status is unclear, but it's not a big plant. China has ambitious plans for the future, but as of now, it appears that China is not producing any plutonium. If it were, it would only be in very small quantities. 

The operation of reactors is visible. When a reactor is turned on, the satellite imagery can show around how much plutonium China has produced. What the Defense Intelligence Agency has said is that even if China converted all of its existing stockpile of military plutonium into weapons, it could roughly double its nuclear arsenal. This would be something like 400 or 500 weapons. That could change in the future, but for now, China does not appear to have enough plutonium on hand to dramatically expand its nuclear arsenal. These numbers are all fairly approximate, but it wouldn’t make a huge difference if the arsenal were 400 or 600 nuclear weapons. Arguably it would matter more if China could build 2,000 or 3,000 weapons. These estimates are not perfect, and there are significant uncertainties. However, a few hundred nuclear weapons here or there, relative to the size of the US arsenal, will not make a huge difference. 

In the lead-up to the Biden administration’s Nuclear Posture Review, how influential will China’s nuclear expansion and modernization be for the United States’ nuclear strategy? 

U.S. Strategic Command, which is the part of the U.S. military that deals with nukes, certainly contributes to the Nuclear Posture Review, though it doesn't write it. U.S. Strategic Command has been making a very, very big deal about China's nuclear weapons. Other people are also clearly worried about China's nuclear weapons, and the U.S. government has openly said that the silo-building is of concern. There are other U.S. officials saying that China is looking at or experimenting with new things, like a nuclear-powered submarine or a nuclear-powered torpedo, to deliver nuclear weapons. 

I expect to hear a lot of noise in the Nuclear Posture Review about China. At the end of the day, though, I would be surprised if the U.S. did anything concrete—in terms of declaratory policy, force structure or acquisitions—that it wouldn't have done had China not been considered to be a nuclear threat. Russia has a much larger nuclear arsenal than China. Russia's nuclear arsenal, particularly in terms of the non-strategic systems, does appear to be improving and perhaps expanding as well. Anything that the U.S has pressure to do for China is probably something that it would have pressure to do for Russia too. Overall, I expect to see a lot of sound and fury when it comes to China and the Nuclear Posture Review. But concrete measures that the U.S. would take for China would have been taken to deal with Russia anyway. 

What impact will China’s nuclear build-up have on other nuclear powers, especially India?  What will Russia’s concerns be? 

India is certainly worried about China's nuclear buildup. It is unlikely India is terribly concerned about the ICBMs because, while China could use them to target India, they are obviously intended for the U.S. The developments in China's regional-range missiles, the shorter-range missiles, are much more concerning to India. I don't know how India is going to respond to this. It certainly could ramp up fissile material production. India has the potential to expand its arsenal significantly. I just don't know whether that's likely, though I wouldn't be surprised either way.  

Moscow is not going to be terribly concerned about this in the short term. Americans like to say that Russia should be worried about China, and there are some Russian officials who may have long-term fears about China. At some level, the Kremlin would probably prefer that China not do this. However, it is not likely to change anything in Russia. Russia is not going to become more pro-American or change its nuclear force posture as a result. Russia is actually working with China on strategic technology, and while the focus is not on nuclear weapons themselves, the Russians are helping the Chinese to develop a strategic early warning system. The Russians wouldn’t do that if they thought there were any chance they would be fighting a nuclear war with China. Americans often exaggerate the implications of Chinese nuclear developments on Russia, which are actually fairly minimal. 

What is the potential for a nuclear arms control dialogue between China and the United States, especially considering China’s historic reluctance to engage in such talks? Does the Chinese nuclear expansion make it more important that China and the United States engage in an arms control dialogue? 

The last part is the easy part. It’s definitely more important.  

In terms of the potential for the talks actually occurring, I'm not optimistic. There are strategic and internal reasons why China doesn't want to talk to the United States. China is generally worried that the more transparent it is, and the more information it gives the U.S. about its nuclear forces, the easier it would be for the U.S. to destroy those nuclear forces in a war. There’s also a more general idea within Chinese thinking that it's up to the strongest state to be transparent, not up to the weaker one. There are also internal bureaucratic barriers in China that I can only guess at.  There is not much experience in this kind of dialogue in China, and therefore there may be a lack of relevant personnel.  

Also, different parts of the Chinese system have different concerns here. What I would say in general is, if there is to be any chance of a dialogue, the U.S. has to think very carefully about what it could offer China. American officials have done a lot of thinking about what China should offer. The Trump administration had this idea of a three-way Arms Limitation Treaty with the U.S., Russia and China. However, when the administration was asked what was in it for China, the only answer they ever came up with was that China will get to have a seat at the big boy’s table. That's not a serious thing that China would want. So, it is necessary to think very carefully about what the U.S. should want to give China in return; there has to be the trade-off of mutual concessions. It is still fairly early in the Biden administration, but I haven't seen much evidence of serious thinking about that yet, so I'm not terribly optimistic. If the U.S. really wants to make an arms control dialogue with China a reality, it has to think about mutual concessions it could provide in return for concessions from China.