Richard Reeve 

31 July 2018

Read the Primer

UPDATE: This primer was first published in July 2018 and updated in May 2019. 


This primer explains the legal and institutional basis of current defence and security relations between the United Kingdom and the United States, including cooperation on nuclear weapons, intelligence-sharing, conventional forces and weapons development and procurement.


The “special relationship” between the United Kingdom and the United States is often referenced by politicians but the reality behind the rhetoric is little understood. While the warmth of personal relationships between prime ministers and presidents may wax and wane, a series of complex and often opaque institutional relationships and infrastructure bind the two countries’ defence and security sectors more closely together than to any other partners. The UK is likely to remain the US’ most capable and valued military and intelligence ally for some time to come, but the relationship is inherently asymmetric given that Washington deploys resources around ten times larger than London’s. This asymmetry has significant impact on the independence of the UK’s conventional and nuclear military forces as well as its involvement in global mass surveillance operations. While at times deeply controversial, as with the economic and legal relationship between the UK and the European Union, unravelling the defence and security relationship with the United States would likely be complex, expensive and involve politically difficult trade-offs.

Key points:

  • The UK and US are bound together legally by the multilateral NATO Charter and a series of bilateral agreements over exchange of intelligence and technology.
  • Cooperation between the UK and US on nuclear weapons development, manufacture and testing is unprecedented and may breach Non-Proliferation Treaty (NPT) obligations.
  • Intelligence-sharing is probably the closest institutional relationship and provides the US with access to a global network of mass surveillance facilities in the UK and British Overseas Territories.
  • The US military also uses several air and naval bases in the UK and overseas territories, including the depopulated Diego Garcia atoll, notably for supporting nuclear-capable strategic bombers and submarines.
  • British desire to be a “full-spectrum” military partner to the US at least partially determines the structure of UK forces, including a deployable Army division, aircraft carriers and nuclear weapons.
  • The UK is the US’ closest military industrial and scientific partner, not least in the F-35 Joint Strike Fighter project. While the British military is increasingly reliant on imports from the US, British industry partners at least as much with European as with US peers.


Image credit: The White House/Public Domain.  

About the Author

Richard Reeve is ORG's Chief Executive and the Director of the Sustainable Security Programme.