Why are the “Five Eyes” called the “Five Eyes”?
All intelligence is graded by a number of factors including security classification. This can range from “Confidential” all the way up to “Top Secret”. Once one gets beyond the “Top Secret” barrier there is often a need for further classification. So, for instance, if the UK produces an intelligence report that it does not wish to share with anyone else, it will be graded “Top Secret UK Eyes A” (there is also “UK Eyes B” which means that the report can be made available to a slightly wider group of UK agencies.) When sharing secret or top secret intelligence with allies, these reports may also be restricted. One that intelligence officers frequently see is “UK/US Eyes Only”.
There is one allied security classification that is most common. That is reports that are graded “UK/US/Can/Aus/NZ Eyes Only”. This is the group who are known as the “Five Eyes” because of this classification wording at the top of their reports. Only their officers (and customers) can see these reports.
This group arose during and immediately after the Second World War. Its roots were in communications intelligence. Intercepting world-wide communications in the days before satellites required ground based listening stations all around the world. By combining US and UK Commonwealth territories, it was possible to provide this coverage. The same group soon became useful for the dissemination of other intelligence as all these countries were, broadly, on the same side. Most Joint Intelligence Committee (JIC) reports produced in the UK will have an input from representatives of all of the “Five Eyes” members.
That is not to say that there is always agreement between the members. Because the government of New Zealand banned nuclear powered vessels from its waters in 1984, the United States insisted that any “Five Eyes” intelligence concerning nuclear matters should no longer be disseminated to New Zealand under the “Five Eyes” agreement. For instance, if such a matter comes up at a JIC meeting, the meeting will be paused while the New Zealand representative is asked to leave. The deabte in 2019 over whether to grant Huawei access to the 5G network also showed differences of approach within the “Five Eyes” network.