What could prompt China to attempt a blockade of Taiwan? If it did so, why is the outcome of such an attempt inherently unpredictable?

I think a blockade is more likely than an invasion attempt, because blockades you can do to varying degrees of seriousness and you don't have to make it airtight. What you could do is occasionally block a ship or sink a ship and see if markets for insurance make other owners of vessels not want to go to Taiwan. In other words, try to target Taiwan's economy more than shutting it off or conquering it. You can do this with submarines that probably won't even be seen, probably won't even be shot at unless the United States decides to try to help out or unless Taiwan decides to escalate it. So I think a blockade, defined as some degree of discouraging or preventing normal shipping and maybe air traffic into Taiwan, is a possibility if China feels that it really needs to send a strong message. In fact, you could already argue that in August 2022, the Chinese walked right up to the edge of a blockade when they retaliated for Speaker Nancy Pelosi's visit by essentially firing missiles and otherwise increasing military activity in the immediate environs of Taiwan. I remember going there the following week, and no one really quite knew if the airplanes were still going to be flying. China was right at the point of being able to change people's calculations about that and could have if they had wanted to do a little bit more, and yet, they still could have stopped short of war, and might not have even had to kill anybody in the process of creating this blockade. Because this option gives China choices, and because China's often historically more interested in using military force to change people's psychology and calculations, rather than going to war, China would be most likely to try a blockade. 

When I looked at it in some detail last year, in a paper that I wrote that you were referring to, I imagined more of an all-out Chinese blockade effort. The trouble for the United States is that this is a hard military operation for us to defeat. We want to reopen those shipping lanes., If you are trying to facilitate Taiwan's trade and open up shipping corridors, you have to protect things that are relatively hard to protect. Whereas for China, they have the opposite situation, all they have to do is occasionally sink the things that are relatively easy to see and sink. And they could do it using just submarines. And then you get into all sorts of uncertainties about if this war really happens. Whose satellite networks are going to survive? What other means do people have of doing surveillance and where are the opposing sides' chips? Or submarines. As I worked through the calculations, I became increasingly convinced there's really no way to be sure based on what we know, even in the classified world, but certainly in the unclassified world, about how well different weapons would perform in this kind of situation, because no one's ever been able to realistically test this kind of  war. We've never had anything like it in human history, with the kind of technologies that are around today. I think it's just too hard to know. And therefore, it could go either way.  I worked through some assumptions where I make assumptions that are deliberately somewhat favorable to China, and I get a Chinese victory. Then, I work through assumptions that are deliberately sometimes somewhat favorable to the United States and Taiwan, but also intended to be realistic and plausible, and that I get to US-Taiwan victory. So that suggests to me even though my model, my mathematical computation is not perfect, it's meant to besort of a distillation of what might really happen or a notional approximation in broad brush to what might happen. Therefore, it could be off, but it still is strongly suggestive that the outcome is unknowable. 

Does China’s recent military modernization efforts and new trends in technology increase the likelihood of a conflict over Taiwan? Is the U.S-China military balance shifting in favor of China?

The military balance certainly has shifted. I mean in relative terms, to some extent, it's more in favor of China and it's shifted in favor of an attack. It’s going to be very hard for either side to protect big fixed or visible infrastructure or ships because both sides are good at precision strikes. They have a lot of weapons, a lot of surveillance capability. Modern technology has just increased the lethality and the accuracy of modern weaponry. So that changes what used to be the case where the United States could dominate in the western Pacific. Even when we were pretty close to China's shores, we could still dominate because we had the more precise weapons or the higher technology airpower, and China didn't have all of it. So yes, you're right. In some sense, China's caught up. But another way to look at it is the technologies that are now available to both sides have made the whole western Pacific a potentially contested zone. It's very hard for me to see how anybody is going to be safe there in a future war. And so while China's not likely to get the advantage over us, I think both sides are going to have a very hard time defeating the other and protecting friendly assets that are visible above the surface, like airfields, ports, and ships.

Why is a Chinese blockade the most likely scenario in a military conflict over Taiwan? What should the U.S. and Taiwan do to best position themselves against possible scenarios of a blockade?

The reason why I think it's more likely compared with an invasion attempt, or essentially a D-Day style attack, like we did in June of 1944, or even in the island campaigns of the Pacific theater against Japan in the 1940s is that today's weaponry is so lethal, and so precise.  Even though Taiwan hasn't yet quite properly prepared its defenses, for China, this is a huge roll of the dice. And the United States may intervene as well. Moving that many ships, potentially more than 100 ships, with weaponry and people aboard, in places where they could be relatively easily targeted, could lead to enormous losses for China. And if they fail, they don't just fail in the sense that Taiwan is now still autonomous. They fail in the sense that they could have lost 30,000-50,000 soldiers and sailors and a lot of equipment. And the whole world could have seen this on CNN. So it's a huge loss of prestige. Whereas with a blockade, you can sort of turn it up and down like a rheostat. And even the more intense blockades don't necessarily lead to a lot of shooting or dying unless the US gets involved and we have a big showdown. But even before that, the Chinese could always back off, let us sort of parade around for a while. And once we get tired and go home, then they turn up the blockade again if they want. So there's the Chinese way of war historically has been again more to use limited amounts of force to affect the psychology of an enemy, rather than to achieve an outright definitive victory. That's not always true. I mean, the Chinese fought for victory in the Korean War against us, for example. So there are times where they fight to take land. But in the period since, the Chinese really haven't fought a large scale war to gain territory. And their goal has typically been to use force as they did against Vietnam in 1979, which is the last real big fight they had used force to intimidate, coerce, or otherwise affect the psychology of the enemy. And a blockade allows for a lot of options on how to do that.

How has modeling and wargaming helped to provide insight into the China-Taiwan conflict?

This is a hard military balance to understand because if we ever fought China again, there'd be so many moving parts. It wouldn't just be, ships shooting at ships and airplanes shooting at airplanes; they'd all be shooting each other. Ships would be informed by airplanes in the sky and satellites overhead trying to gain information about the location, as well as other methods each side would use to try to interfere with the satellites and the communications of the other. And undersea warfare would be very powerful. All these things in combination have never really been seen before in warfare. For example, in World War Two, yes, you had ships, planes and subs, but you didn't have satellites. And you didn't have precision weapons of the type we have today. World War Two was difficult enough to understand and it took numerous twists and turns, as different sides figured out better tactics. So this would be so complicated of a conflict. Again, the United States has done a lot more fighting this century than the Chinese. But we've been fighting the Taliban and al Qaeda. And we have not been fighting a modern, technologically sophisticated enemy. So we're not very good at that. We don't know how that would work. We're trying to think more about how to do that. So hopefully, the Chinese won't think that we're incapable, and then decided they could launch an attack against us because we're prepared for the wrong enemy or for the wrong war. So we got to stay very vigilant, we should be very humble about our ability to understand what that future war would look like. And the Chinese should be humbled too. But unfortunately, in history, oftentimes, countries forget all the things that could go wrong with their beautiful war plans. And sometimes they convince themselves they've got some new weapons, some clever ideas, some brilliant leaders, a strong fighting force, and they go ahead and decide to launch a conflict with more confidence than they should have. We better be highly wary of anybody who would say on either side, that they've got an easy path to victory, or a way to understand how this war would play out, because there are just too many moving parts.

In your Brookings study Can China take Taiwan, you discuss two main scenarios: war at sea and expanded war, including missile strikes and air raids. What threshold must be met for the second scenario to occur and how likely is it?

Yeah, so right, I tried, I didn't claim these were the only two scenarios. But I tried to imagine, in the second scenario, an escalation beyond submarine warfare. Let's suppose that whoever's losing that fight, or whoever thinks they might lose that fight, decides to escalate and start going after the home base of each country, or the main operating bases from which the submarine sail,  and take some more risk that by attacking the Chinese homeland. If we did that, or the Chinese attack Japanese bases, the other side might get so angry that it escalates and we even run the risk of a nuclear war. So that's why I thought it was important to start with a more constrained scenario and then consider a larger one. But we should not be overconfident that things would stay limited because whoever starting to lose or whoever thinks they might lose, has a strong incentive to escalate if that war ever begins.  I think wars between major powers are very hard to stop once they start, because there are always multiple ways for each side to decide that if it's losing, it can change its approach or bring in new weapons or expand the geographical theater, or in the case of the United States and China even threatened nuclear weapons use against the other and perhaps even carry out a nuclear attack. In that sense, it's just scary to think of how this war could blow up. And the two specific scenarios that I gave are by no means the end of the story. In fact, even the second one, which does presuppose these attacks against, let's say, Chinese ports, or Chinese attacks against Japanese bases that we use. I'm assuming only conventional weapons are used and the war stays limited to the area a few 100 miles around Taiwan, neither of those assumptions may prove to be correct. I could very easily have had a third scenario, which is one that could lead to all out World War Three or nuclear war. And I would have no confidence that we would avoid that if this war begins. So one more reason for people to be extremely cautious about ever firing the first shot.

As we move into 2023, how can the US and Taiwan leverage modeling and wargaming to prepare for an escalation of tensions and possible conflict in the future? What are some potential next steps these countries should take?

Well, modeling and wargaming is good, but it's not only to suggest it's the whole enchilada. I wrote that paper last summer, but before that, I had done a book on military history. And I didn't try to do any modeling of the wars that had already happened. I just tried to  tell the major events and put in context as to how these wars began and how they ended and the major decisions that were made along the way. I think that kind of study is equally important because when you read history, it is sobering to remember how often people went to war with an unrealistic expectation of their prospects for success and especially for rapid success. So modeling and simulation are good, because they allow you to try to bring into play the effects of new weapons and technologies, and  update what you learned from history for the modern world. But also just reading and studying history and reflecting on it is important because history is our database of how humans fight. That's what the history of military engagements amounts to; it is the entirety of our database, from which we can hopefully draw some conclusions about the way the human brain and human organizations tend to behave in conflict. In that sense, I believe just as much in studying history, as I do in modeling and wargaming. But I believe in all of it, because the important thing is to make sure that if we ever have a leader on either side, who has been naive about what a war could look like, that we have multiple ways of informing that leader, that in fact, there are huge uncertainties and dangers here, no matter who strikes first, no matter who has the better hypersonic weapons or artificial intelligence, no matter who thinks they've got the more clever war plan. A lot of times in history, when people went to war with that belief, they wound up being wrong. Maybe the first week or the first month of war went pretty well for them. But then they ran out of gas or the other side adapted. And next thing you know, you've got a five-year long conflict, like we see perhaps in Ukraine today. So, again, history as a way of reminding ourselves of the kinds of mistakes that humans tend to make when they go to war would be equally important to modeling and wargaming.