Amendments to the UK-US Mutual Defence Agreement
Parts of the UK-US Mutual Defence Agreement, which underpins nuclear cooperation between the two countries, will expire in December 2024.
In January 2017 newly inaugurated US President, Donald Trump, signed an Executive Order which, among other things, called for a review of US nuclear policy, strategy, capabilities and force posture. That Nuclear Posture Review was published in February 2018. As widely expected, deterrence and not disarmament was the overriding message of the Trump review, and a marked departure from key nuclear policies under the Obama administration that sought to lower the reliance on nuclear weapons and embrace non-proliferation and disarmament.
President Trump: The Nuclear Question (514 KB , PDF)
In January 2017, newly inaugurated President Trump called for a new Nuclear Posture Review (NPR) to examine US nuclear policy, strategy, capabilities and force posture to ensure that it is appropriately tailored to 21st century threats.
The last examination of US nuclear policy was in 2010 and was widely viewed as a mechanism through which President Obama’s vision of ‘Global Zero’, a world without nuclear weapons, could be pursued. For the first time in US nuclear history, it gave primacy to the threat of nuclear proliferation and nuclear terrorism, as opposed to a nuclear exchange between nations. As such, one of its main aims was to reduce the role and scope of nuclear weapons in US policy policymaking.
Despite the ‘disarmament’ overtures of the 2010 NPR, by the end of the Obama administration the US government had set in train a series of nuclear modernisation programmes across the whole of the nuclear triad, which are estimated to cost approximately $1.2 trillion over the next 30 years.
Nuclear Policy under Trump
During both the election campaign and in his first year in office, there appeared to be a distinct lack of clarity on Trump’s nuclear vision which raised interesting questions for the strategic direction of his NPR. Would it build upon the disarmament vision espoused by the Obama administration? Or would it be more assertive in tone, in line with his guiding foreign policy principle of “America first”?
The NPR was published in February 2018. As widely expected, deterrence and not disarmament is the overriding message of the Trump review, and a marked departure from key nuclear policies under the Obama administration that sought to lower the reliance on nuclear weapons and embrace non-proliferation and disarmament.
Echoing the conclusions of the Trump administration’s National Defense Strategy, the 2018 NPR acknowledges the re-emergence of long term ‘great power’ competition as a defining feature of the strategic environment, along with the threats posed by the nuclear ambitions of North Korea and Iran and by nuclear terrorism.
To that end, the focus of the 2018 NPR is on deterrence, albeit through a new lens. The nuclear triad, supported by a robust nuclear command and control system is considered to continue offering the most cost-effective means of ensuring strategic deterrence. As such, the modernisation programmes begun under the Obama administration are fully supported. However, the NPR also emphasises the need to maintain flexibility in any nuclear response, given “the range of adversaries, their capabilities and strategic objectives”, noting that a “one size fits all” approach no longer applies. In a major departure from the 2010 review, the 2018 NPR therefore states the intention to introduce new “flexible”, non-strategic, options into the US nuclear inventory in order to provide tailored deterrence.
The NPR also expands the definitions underpinning the US’ declaratory policy to include significant non- nuclear strategic attacks, including cyber, on critical infrastructure and civilian populations, and attacks on US or allied nuclear forces, including command and control and warning and attack assessment capabilities, as an “extreme circumstance” that would warrant a nuclear response.
While committing the US to the longer-term goal of disarmament, the NPR also adopts a heavily caveated approach to future arms control, suggesting that “further progress is difficult to envision” and that the US would “remain receptive to future arms control negotiations if conditions permit and the potential outcome improves the security of the United States, its allies, and partners”. It does little to address alleged Russian non-compliance with the Intermediate Nuclear Forces Treaty and offers no proposals for moving negotiations forward on the extension of New START, or any potential successor arms control treaty. The NPR also confirms that ratification of the Comprehensive Test Ban Treaty is no longer a policy objective under the Trump administration. It does, however, confirm the US’ intention to maintain its moratorium on nuclear testing.
Reactions to the NPR have been mixed. While many have been supportive of what they regard as a continuation of many of the US’ longstanding nuclear policies, others have been critical of decisions that will add capability to the US nuclear inventory and could potentially lower the nuclear threshold.
President Trump: The Nuclear Question (514 KB , PDF)
Parts of the UK-US Mutual Defence Agreement, which underpins nuclear cooperation between the two countries, will expire in December 2024.
This briefing collates all the reports published by the Defence Committee, Public Accounts Committee and the National Audit Office between May 2010 and May 2024 and reflects the period the Conservative Party was in government.
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