Nuclear and Non-Nuclear Deterrents

Ukraine's options for deterring Russia in the future.

This week offered some key insights into Ukraine's perspective on a future deterrence relationship with Russia and how Kyiv plans to prevent another invasion.

Zelensky’s preferred option likely remains credible security guarantees from Western nuclear powers, most notably through NATO membership.

Other possibilities include developing an independent nuclear deterrent or pursuing a 'non-nuclear strategic deterrent’, as announced by Zelensky in recent days. These options could serve as alternatives to NATO membership or be pursued alongside joining the alliance.

A nuclear deterrent

Ukrainian nuclear weapons would arguably constitute a very credible deterrent in a post-war world. The problem for Kyiv is that there are major technical, political, and military obstacles in the way of fielding such a nuclear deterrent.

First, while Ukraine very likely retained Soviet designs for manufacturing nuclear warheads, Ukraine does not have access to the needed fissile material to build a bomb.

As I have outlined in a previous post, there are two pathways to acquiring nuclear fissile material: a uranium and plutonium route. Ukraine does not possess uranium enrichment facilities, meaning it would have to go down the plutonium route.

The plutonium route involves using a nuclear reactor to irradiate uranium, which absorbs neutrons and transforms into plutonium-239 (Pu-239). After sufficient buildup, the spent reactor fuel is chemically reprocessed to extract Pu-239.

Ukraine currently neither fields ‘breeder’ reactors optimized for creating Pu-239, nor does it deploy reprocessing facilities, meaning it has no way to extract the fissile material. Ukraine could of course build up this capacity, but doing so would take time.

Attempting to proliferate would likely not remain secret, as the International Atomic Energy Agency (IAEA) enforces safeguards on Ukrainian nuclear facilities to ensure Ukraine's civilian nuclear program isn't repurposed for military use.

Any significant deviation from standard nuclear power operations, such as optimizing for Pu-239 production through a low burn-up process for fuel rods, would trigger immediate scrutiny. This would likely result in the IAEA notifying member states of potential nuclear proliferation concerns.

In turn, this could result in a large-scale Russian missile strike on Ukraine's nuclear energy infrastructure under the pretext of preventing Ukrainian proliferation. In this context, international condemnation may be minimal.

Ukraine could technically avoid IAEA scrutiny by formally withdrawing from the Nonproliferation Treaty and expelling IAEA observers and equipment from its facilities. However, this would likely lead to the same outcome. International observers would interpret such actions as a clear intent to proliferate, prompting a preventive strike by Russia.

This doesn't mean it's fundamentally impossible for Ukraine to acquire a nuclear weapon. However, it would require a longer-term effort. In any case, Ukraine must assume that Russia would have little hesitation in conducting a counter-proliferation strike if they see the need, even after this war is over.

A non-nuclear deterrent

A credible non-nuclear deterrent could be a viable alternative. Zelensky suggested this in his peace plan, which included a "non-nuclear strategic deterrent package”. Importantly, this capability was mentioned in the context of Ukraine joining NATO, but could also bolster Kyiv’s deterrence posture outside of NATO membership.

We don't know what exactly Zelensky means by this, but we can speculate. The terms "non-nuclear strategic weapon" or "strategic non-nuclear weapon" first emerged in academic literature to describe the decreasing gap in lethality between nuclear and conventional weapons.

The idea is that certain non-nuclear weapons, particularly conventional long-range strike weapons, can sometimes substitute for nuclear weapons. Ukraine is likely hinting at attempting to replicate the punitive effects of nuclear weapons using conventional missile capabilities.

One possibility is that Ukraine aims at deploying a long-range strike capability that can credibly hold at risk a significant share of Russian critical civilian infrastructure, including electricity, transportation, oil reprocessing and storage, gas extraction, and other key industries, in order to deter Russian aggression.

The idea would be to convey that once a Russian attack begins, Ukraine will immediately retaliate by significantly degrading Russia's economic potential and output, substantially reducing its GDP.

Ukraine has demonstrated that it is capable of developing and manufacturing long-range strike weapons that can be used for these types of purposes. However, to move beyond a minimum-credibility conventional countervalue posture, Ukraine would likely need to expand its arsenal beyond long-range one-way attack drones and incorporate a significant number of short- to intermediate-range ballistic missiles as well as longer-range land-attack cruise missiles.

Credibility challenges

Nuclear proliferation seems an unviable option for Ukraine, especially in the short to medium term, and especially in the context of the ongoing war. It presents not only technical challenges but also significant political and military risks.

A possible alternative, deploying a non-nuclear strategic deterrent to implement a conventional countervalue posture is also challenging, but arguably much more feasible. Simply by advancing its long-range strike capabilities, Ukraine will naturally move in its direction.

The key question is how targeted the Ukrainian effort will be to employ its long-range strike arsenal as a strategic deterrent, rather than as a simple warfighting tool, and how much money Kyiv is willing to allocate to this end over other competing priorities.