Rod Lyon ^[1] and Malcolm Davis ^[2] superbly articulate the inherent risk of declaratory policy—just because you limit yourself with regard to nuclear weapons doesn’t mean that your adversaries will benevolently respond in-kind. I agree that it may be unsound categorically to rule out nuclear first use in absolutely all circumstances. One of the benefits of a multilateral treaty prohibiting low-yield nuclear weapons over sole purpose is that it raises the nuclear threshold without setting an inflexible condition on nuclear use.

I’ll try to address the specific questions posed by Rod with regard to Baltic and China. First, how does making it clear to Putin that the United States would not contemplate initiating a nuclear conflict to defend the Baltic states enhance Lithuania’s security, even if an unlikely prospect?

The answer turns on a philosophical point. There are some who believe (and I’m not suggesting Rod or Malcolm are in this category) that questioning nuclear deterrence weakens it. I don’t. Nuclear deterrence must stand or fall on credibility and nothing else. If questioning the credibility of nuclear use in certain cases makes actual use less likely, chances are that any security benefit was illusory to begin with. That doesn’t mean the United States should declare redlines (or make sole-purpose declarations), but clarity about when nuclear use is more or less credible helps avoid catastrophic miscalculations and focuses attention on what provides a real security dividend.

In the case of Lithuania specifically, since the United States knows that it’s not going to use nuclear weapons to defend it, and since the Russians know this too, the only people who don’t know are the Lithuanians. What would really provide credible assurance to Lithuania is a much larger deployment of US and NATO troops on Lithuanian soil to deter or defeat a conventional Russian attack. It certainly wouldn’t do Lithuania any favours were those assets to be withheld on the basis of some vague and incredible nuclear assurance.

With regard to the US–China scenario, Rod appears to make both our cases. Yes, China is presently modernising and expanding its nuclear forces, which is precisely what is to be expected given America’s first strike nuclear posture and the proliferation of ballistic missile defences. I agree with Rod that this hinders any move towards sole purpose, and just to be clear I’m advocating multilateral, not unilateral, action on nuclear arms control. But if America reflexively doubles-down on nuclear deterrence without any nuclear arms-control strategy whatsoever then I want to know how America intends to halt nuclear proliferation when, as is foreseeable, China ends up with a nuclear arsenal of comparable size to its own.

Of course, Rod is absolutely correct to say that China’s neighbours are currently more preoccupied with China’s conventional arms build-up. The inconvenient truth is this: there’s no simple answer to China’s conventional military expansion, but we should do all we can proactively to mitigate its risks. If that strategy fails, as well it may, it will be tragic for us and the world—but an overly-aggressive US nuclear posture will do nothing to prevent that, and potentially much to hasten it.

Rod’s last question is, how does it make Asian allies feel safer for the United States to remove the first use of nuclear weapons from its repertoire? Again, I would put a multilateral treaty prohibiting low-yield nuclear weapons ^[3] much higher on the agenda, but the substantive answer is this: that America needs to take a broader strategic view than just whatever makes its allies (including us) feel better at a given point in time. The question before us is not what would make us slightly more or less anxious today; rather, how anxious we will feel when China possesses a vast nuclear arsenal and abandons its no-first-use doctrine, and what compromises we are willing to make in order to offset that eventuality.

Crispin Rovere is a former PhD student at the Strategic and Defence Studies Centre, ANU and co-author of Non-strategic nuclear weapons: the next step in multilateral arms control.