Russian nuclear sabre-rattling following the 2022 invasion of Ukraine has reinvigorated debates over NATO deterrence. One of its key components—nuclear sharing—has been in place since September 1954, but support for it within the alliance has varied over time. Indeed, although Belgium, Germany, Italy, the Netherlands and Turkey host American gravity bombs on their territory, there were fears during the 2010s that some of them would follow Canada, Greece and the United Kingdom's example and withdraw from the scheme. By examining why and how NATO's nuclear-sharing arrangements have changed since inception, we argue that they consistently serve deterrence, signalling, alliance cohesion and burden-sharing goals, which make them hard to dismantle. However, we also demonstrate, through our survey of post-Cold War policies, official statements and public debates, that there is more room in a low threat environment for political contestation within host states. Accordingly, nuclear sharing requires a high threat environment to escape domestic opposition, which effectively returned in 2022, cementing the nuclear status quo.

中文翻译：

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乌克兰战争和北约核共享

2022 年入侵乌克兰后，俄罗斯的核武力威胁再次引发了有关北约威慑力的争论。其关键组成部分之一——核共享——自 1954 年 9 月起就已经到位，但联盟内部对其的支持随着时间的推移而变化。事实上，尽管比利时、德国、意大利、荷兰和土耳其在其领土上部署了美国重力炸弹，但在 2010 年代人们担心其中一些国家会效仿加拿大、希腊和英国的做法，退出该计划。通过研究北约核共享安排自成立以来发生变化的原因和方式，我们认为它们始终服务于威慑、信号、联盟凝聚力和分担负担的目标，这使得它们难以拆除。然而，通过对冷战后政策、官方声明和公开辩论的调查，我们还表明，在低威胁环境下，东道国内部存在更大的政治竞争空间。因此，核共享需要高威胁环境来逃避国内反对，这种反对实际上在 2022 年卷土重来，巩固了核现状。