POLICY
Nuclear Weapons, Military Alliances, and the Fall-Out of the Russo-Ukrainian War
May 10, 2023
Russia’s full-scale invasion of Ukraine has upended the international security environment. Beyond the trauma and damage that this invasion has caused for Ukrainians, Russia’s military aggression has reignited concerns about territorial aggression amongst many of United States’ own treaty allies, especially those in Europe. If Russia were to succeed, then they might be next in its crosshairs. For those U.S. allies further afield, such as those in East Asia, Russia’s war-making suggests that norms of territorial integrity are perhaps not as strong as once believed. China might be drawing its own lessons for any sort of contingency involving Taiwan or some other dispute with its neighbors.
The consequent insecurity has thus occasioned some reflection on the connection between military alliances and nuclear proliferation. After all, Ukraine is only a partner to the North Atlantic Treaty Organization, rather than a formal member. Partly because it does not receive any security commitments like that expressed in Article 5 of the Washington Treaty, Ukraine fights Russia alone. Had it been a member of NATO, as many advocate it should be, perhaps Russia would have been deterred from launching its assault on the first place. Moreover, Ukraine disavowed nuclear weapons in the early 1990s to have good standing with the international community and to receive promises regarding its own territorial integrity. Although it never had a proper nuclear deterrent, its brief inheritance of nuclear weapons following the breakup of the Soviet Union has led some observers to believe that Ukraine’s nonproliferation commitments proved to be mistaken. No country possessing nuclear weapons has been the victim of such violence of the sort that Ukraine has been suffered lately.
These debates feature major counterfactuals, but at the heart of the matter is a sense that military alliances and nuclear proliferation bear some deep connection to one another. And indeed, because countries might be worried about being the next to come under major attack, they might reconsider the value of nuclear weapons in a way that might have been politically unacceptable not long ago. In a world of self-help, even treaty allies might come to see nuclear weapons as their best guarantee. And if more countries get nuclear weapons, the likelihood of their use rises accordingly.
As I show in my book Atomic Assurance, however, the relationship between military alliances and nuclear weapons is hardly linear. Being within a military alliance—with the United States no less—is often better than being without. A received security guarantee involving a nuclear-armed power could force potential adversaries to think twice about attacking, especially if it runs the risk of triggering retaliation that carries with it unacceptable costs. Allies, therefore, have reasons not to seek nuclear weapons. That said, no state can ever be entirely sure that others, including its treaty allies, would come to its assistance in wartime. The cost of direct military involvement, regardless of whether nuclear weapons could get used, can be extraordinary. States facing down a major threat, particularly one already armed with nuclear weapons, might discount the protection that an alliance might seem to offer and so decide to seek their own nuclear weapons.
What is the empirical record? Most treaty allies of the United States do not have a nuclear weapons arsenal. Only Great Britain and France do, and they made their decisions to acquire such capabilities at a time when they still had empire abroad and the international norms about nuclear weapons were inchoate. Nevertheless, various U.S. treaty allies undertook some activities that were at least suggestive of an interest in nuclear weapons, if they not did have an active, dedicated program. South Korea had one such program. Other countries—like Japan and West Germany—invested in capabilities that gave them the option, at times conveying a sense of ambiguity over their long-term nuclear intentions.
In cases like South Korea and West Germany, what stirred their interest was a sense that their received security commitments from the United States were fundamentally broken. For Seoul, President Richard Nixon’s unexpected decision to withdraw the 7th Infantry division from the Korean Peninsula was powerful evidence that the United States was withdrawing from East Asia, especially as it articulated a foreign policy that sought to offload the conventional defence burden on allies as part of a larger strategy to get out of Vietnam. The U.S. commitment to Europe was itself under duress throughout the 1960s. Despite large numbers of troops stationed on the continent, which in turn showed that the United States ‘skin in the game’ and would make any war-making by the Soviet Union extremely risky, West German leaders received many signals that the United States might yet pull back.
Of course, the United States would to this day retain a large troop presence on their territory and those countries do not possess nuclear weapons. That the United States stayed is indeed only part of the explanation for those states’ decisions not to seek nuclear weapons. Each case of nuclear proliferation has its own peculiarities, but domestic political change, leadership turnover, and a shifting international environment would come to dampen what interest those states might have had in sensitive nuclear materials. With varying degrees of success, the United States also pressured those countries to make firm nonproliferation commitments.
These cases all come from the Cold War, but past may be prologue. It is true that many cases of nuclear proliferation—especially those involving democracies—unfolded when norms about nuclear weapons were under-developed relative to what we have today. Still, those cases do indicate that there is some link between military alliances and nuclear proliferation.
As concerns intensify about territorial aggression and the stakes thus ratchet up, even treaty allies of the United States would be evaluating their received security guarantees with greater scrutiny than before. Specifically, if the United States weakens its international commitments, especially in a manner that is abrupt and unilateral, affected allies might be so alarmed as to think that nuclear weapons offer a valid alternative that might be worth pursuing. This hypothetical may possibly become reality. Not only has it happened in the past during the Cold War, but the renewal of isolationist sentiment and a weariness of engagement abroad in the U.S. body politic could yet produce a president willing and able to make alliance adjustments.
These debates feature major counterfactuals, but at the heart of the matter is a sense that military alliances and nuclear proliferation bear some deep connection to one another. And indeed, because countries might be worried about being the next to come under major attack, they might reconsider the value of nuclear weapons in a way that might have been politically unacceptable not long ago. In a world of self-help, even treaty allies might come to see nuclear weapons as their best guarantee. And if more countries get nuclear weapons, the likelihood of their use rises accordingly.
As I show in my book Atomic Assurance, however, the relationship between military alliances and nuclear weapons is hardly linear. Being within a military alliance—with the United States no less—is often better than being without. A received security guarantee involving a nuclear-armed power could force potential adversaries to think twice about attacking, especially if it runs the risk of triggering retaliation that carries with it unacceptable costs. Allies, therefore, have reasons not to seek nuclear weapons. That said, no state can ever be entirely sure that others, including its treaty allies, would come to its assistance in wartime. The cost of direct military involvement, regardless of whether nuclear weapons could get used, can be extraordinary. States facing down a major threat, particularly one already armed with nuclear weapons, might discount the protection that an alliance might seem to offer and so decide to seek their own nuclear weapons.
What is the empirical record? Most treaty allies of the United States do not have a nuclear weapons arsenal. Only Great Britain and France do, and they made their decisions to acquire such capabilities at a time when they still had empire abroad and the international norms about nuclear weapons were inchoate. Nevertheless, various U.S. treaty allies undertook some activities that were at least suggestive of an interest in nuclear weapons, if they not did have an active, dedicated program. South Korea had one such program. Other countries—like Japan and West Germany—invested in capabilities that gave them the option, at times conveying a sense of ambiguity over their long-term nuclear intentions.
In cases like South Korea and West Germany, what stirred their interest was a sense that their received security commitments from the United States were fundamentally broken. For Seoul, President Richard Nixon’s unexpected decision to withdraw the 7th Infantry division from the Korean Peninsula was powerful evidence that the United States was withdrawing from East Asia, especially as it articulated a foreign policy that sought to offload the conventional defence burden on allies as part of a larger strategy to get out of Vietnam. The U.S. commitment to Europe was itself under duress throughout the 1960s. Despite large numbers of troops stationed on the continent, which in turn showed that the United States ‘skin in the game’ and would make any war-making by the Soviet Union extremely risky, West German leaders received many signals that the United States might yet pull back.
Of course, the United States would to this day retain a large troop presence on their territory and those countries do not possess nuclear weapons. That the United States stayed is indeed only part of the explanation for those states’ decisions not to seek nuclear weapons. Each case of nuclear proliferation has its own peculiarities, but domestic political change, leadership turnover, and a shifting international environment would come to dampen what interest those states might have had in sensitive nuclear materials. With varying degrees of success, the United States also pressured those countries to make firm nonproliferation commitments.
These cases all come from the Cold War, but past may be prologue. It is true that many cases of nuclear proliferation—especially those involving democracies—unfolded when norms about nuclear weapons were under-developed relative to what we have today. Still, those cases do indicate that there is some link between military alliances and nuclear proliferation.
As concerns intensify about territorial aggression and the stakes thus ratchet up, even treaty allies of the United States would be evaluating their received security guarantees with greater scrutiny than before. Specifically, if the United States weakens its international commitments, especially in a manner that is abrupt and unilateral, affected allies might be so alarmed as to think that nuclear weapons offer a valid alternative that might be worth pursuing. This hypothetical may possibly become reality. Not only has it happened in the past during the Cold War, but the renewal of isolationist sentiment and a weariness of engagement abroad in the U.S. body politic could yet produce a president willing and able to make alliance adjustments.
