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Five Eyes intelligence alliance
UKUSA agreement 1946· Alliance or organization
FactTreaties, membership, measured data, events.
The intelligence-sharing alliance of the US, UK, Canada, Australia and New Zealand, rooted in World War II codebreaking.
See it on the Geopolitics map →The picture
Wartime cooperation between Britain's Bletchley Park and US codebreakers became the 1946 UKUSA agreement; Canada joined in 1948, Australia and New Zealand in 1956. Their signals agencies (NSA, GCHQ, CSE, ASD and GCSB) divide up the globe, share intercepts and much analysis, and reportedly agree not to spy on each other. Its founding texts were declassified only in 2010; Edward Snowden's 2013 leaks exposed its reach. Under Trump some sharing has been limited, reportedly including on 2025 Russia–Ukraine talks.
Why it matters
It is the world's deepest intelligence partnership and a core advantage of the US alliance system, especially in tracking China and Russia.
Key facts and numbers
Declassified UKUSA documents released in 2010, the Snowden files, and joint public appearances such as the five intelligence chiefs' 2023 warning about China.
What to watch
Outlook: whether trust survives US–ally rifts over tariffs, Greenland and Caribbean boat strikes, and whether Japan should join; members disagree.
Connections (2)
▸Canada is a member of Five Eyes intelligence allianceFact
The relationship
Canada joined the UKUSA signals-intelligence pact in 1948. Its Communications Security Establishment covers assigned regions, including the Arctic, and shares intercepts with the others, giving Ottawa intelligence far beyond what it could gather alone. Trade fights with Washington in 2025 raised talk of strain.
Since when and why
Ottawa and Washington, from 1948; in February 2025 White House adviser Peter Navarro reportedly floated expelling Canada, and nothing came of it.
How we know
Declassified UKUSA records, Canadian government statements on CSE's role, and Financial Times reporting on the Navarro idea.
What to watch
How much US–Canada political tension affects daily sharing; officials on both sides say the intelligence relationship remains intact.
▸United Kingdom is a member of Five Eyes intelligence allianceFact
The relationship
Britain co-founded the alliance: its wartime codebreaking partnership with the US became the 1946 UKUSA agreement. Its signals agency GCHQ shares intercepts with the NSA, and US-run stations in Britain such as Menwith Hill are part of the network, giving the UK intelligence reach far beyond its size.
Since when and why
London and Washington, March 5, 1946, building on Bletchley Park cooperation in 1941–45.
How we know
The UKUSA agreement, declassified and published by GCHQ and the NSA in 2010, and the Snowden documents of 2013.
What to watch
Reports in late 2025 that Britain paused some Caribbean intelligence over US boat strikes raised questions about legal limits on sharing; London declined to discuss details.