Born out of World War II, it’s the world’s deepest and most comprehensive collaboration among spy services. But now the U.S. has threatened to limit the intelligence it supplies to the so-called Five Eyes network unless its members join it in excluding equipment from Chinese telecommunications giant Huawei Technologies Co. from their new 5G mobile networks.

1. What is Five Eyes?

The Five Eyes name refers to the security classification of intelligence documents: SECRET – AUS/CAN/N.Z./U.K./U.S. EYES ONLY. It began in 1946, when the U.S. and the U.K. agreed to institutionalize the intelligence sharing that helped them win the war; the U.K. had broken Germany’s Enigma code, giving it access to German war communications, while the U.S. had cracked Japan’s Purple cipher. Canada joined the club two years later, and Australia and New Zealand in 1956. The group is so good at keeping secrets that its existence was only revealed to the public in the mid-2000s.

2. What’s shared?

It’s not clear, but a lot. Most of whistle-blower Edward Snowden’s vast 2013 dump of classified U.S. National Security Agency data was marked “FVEY’’, making it available to other Five Eyes members. At the network’s inception, the U.S. and U.K. agreed to unrestricted exchange of intelligence on the communications of foreign nations. At the time, this meant mostly radio signals and phone calls intercepted in pursuit of the Cold War. The deal allowed the two countries to rely on each other’s listening posts around the world, without having to duplicate infrastructure, and to track nuclear armed Soviet submarines. Open source research suggests that the five national agencies still divide the world into zones of specialization, to maximize their resources. But with the advent of the internet, the communications monitored have expanded exponentially. Advocates say the collaboration has been critical to international security, used to positive effect in the Afghanistan war as well as in counter-terrorism operations in the Philippines and East Africa.

3. What is the U.S. worried about?

That if the new, super-fast 5G networks being put in place around the world are constructed using Huawei equipment, the Chinese government and its spy agencies could be given a window into the systems. 5G will eventually connect far more devices than currently available data networks; the U.S. is warning other countries that Huawei 5G equipment, chips and software, could be outfitted by Chinese intelligence agencies to spy on them. The more American intelligence is shared, the greater the risk that it could find its way to Beijing. Huawei has always denied that any of its equipment has been compromised, and no evidence has been brought forth showing that it has.

4. What’s the U.S. doing about it?

Leaning heavily on its allies in general and on the members of Five Eyes allies in particular. In February, Secretary of State Mike Pompeo warned Five Eyes member New Zealand that the U.S. would not share information with it, if the country included Huawei in its “critical information systems.’’ In April, he delivered the same message to NATO allies, and in May he warned the U.K. specifically not to “go wobbly’’ on Huawei exclusion. In public, U.S. President Donald Trump diplomatically glossed over the issue, answering “no” when asked during a press conference in London if whether the U.K. could be cut off from U.S. intelligence over the dispute. “We have an incredible intelligence relationship, and we will be able to work out any differences,” he said.

5. How have the other Five Eyes alliance members responded?

The U.K. has yet to take an official position on Huawei; recently announced U.S. sanctions on the company have complicated and extended a review into the national security of its telecom supply chain. Canada has yet to make a decision on restricting or banning the company, and has put the issue on the back burner, said Canadian Public Safety Minister Ralph Goodale. Australia and New Zealand have already taken steps to restrict Huawei’s access, making Pompeo’s warning-- 5G or Five Eyes-- aimed squarely at the U.K. and Canada. Huawei is favored by some telecommunications companies for its technological edge and low cost.

6. Are there downsides to Five Eyes sharing?

Whistle-blower Edward Snowden’s 2013 disclosures showed that the U.S. was gathering and holding huge amounts of data on its own citizens, and raised concerns that some of it was being being gleaned from the Five Eyes network. In essence, critics said, Five Eyes was allowing the U.S. to circumvent restrictive domestic surveillance laws by borrowing from its allies. In response, President Barack Obama announced in January 2014 that the NSA’s surveillance programs would be overhauled, including introducing new rules about how signals intelligence collected abroad could be used. Snowden attacked Five Eyes as a supranational organization, unanswerable to democratic oversight by its respective national governments.

(Fixes spacing typo in second paragraph.)

To contact the reporter on this story: Emma Vickers in New York at evickers4@bloomberg.net

To contact the editors responsible for this story: Leah Harrison Singer at lharrison@bloomberg.net, John O’Neil, Bill Faries

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