https://thebulletin.org/wp-content/uploads/2021/04/Vanguard_at_Faslane_04-featured-image-150x150.jpg Editor’s note: The Nuclear Notebook is researched and written by Hans M. Kristensen, director of the Nuclear Information Project with the Federation of American Scientists, and Matt Korda, a research associate with the project. The Nuclear Notebook column has been published in the Bulletin of the Atomic Scientists since 1987. To download a free PDF of this article, click here. To see all previous Nuclear Notebook columns, click here.
Of all the nuclear weapon states, the United Kingdom has moved the furthest toward establishing a minimum nuclear deterrent. The United Kingdom has a stockpile of approximately 225 nuclear warheads, of which up to 120 are operationally available for deployment on four Vanguard-class nuclear-powered ballistic missile submarines (SSBNs). This estimate is based on publicly available information regarding the size of the British nuclear arsenal, conversations with UK officials, and analysis of the nuclear forces structure. The SSBNs, each of which has 16 missile tubes, constitute the United Kingdom’s sole nuclear platform, and submarine-launched ballistic missiles (SLBMs) comprise its sole nuclear delivery system. The United Kingdom is the only nuclear weapon state that operates a posture with a single deterrence system (Table 1).