Project Arcadia: Why New Zealand signed up to the Five Eyes system
New Zealand committed to Project Arcadia in May, about a month after the Defence Force warned that staying out would cut it off from allied information exchanges.
Newly released briefings show the warning was made in April, while the New Zealand Defence Force was considering whether to help build Arcadia. Brigadier E J Harrop, commander of NZDF Information Command, briefed the Vice Chief of the Defence Force on the proposal, according to the documents RNZ.
The language was direct. The briefings said if NZDF did not commit, it would not have access to foundational capabilities and would be "effectively cut off from future FVEY information exchanges". FVEY stands for Five Eyes, the intelligence-sharing group. A separate briefing said that without joining the Arcadia memorandum of understanding, a formal agreement between governments, New Zealand risked becoming a "lower trust, lower influence partner".
What Arcadia is
Arcadia is the new digital backbone linking the militaries of the five Five Eyes countries. Think of it as shared wiring that lets each military's computers, data and communications work together. The United States announced the build in May. The memorandum of understanding appears to have been signed in May 2026 to set out long-term oversight and funding.
The briefings set out the operational case for joining. They said Arcadia would improve warfighting and intelligence gathering. It would give New Zealand access to emerging technologies and keep its systems aligned and interoperable with other Five Eyes countries. Interoperable means able to operate together. Joining would let NZDF go well beyond what it could afford alone, without loss of national control, the briefings said.
New Zealand was not a latecomer to the idea. It helped develop the Arcadia concept when it led a key Five Eyes information group in 2024-25.
What it will cost
Cost is still not settled. NZDF had spent about $3 million on Arcadia by April, according to the documents. An April document said the spread of costs was not known and a US programme office was working on costs. A briefing said Defence would need to seek extra funding in Budget 2027 for a build expected to take six years. That bid will sit alongside New Zealand's $12 billion Defence Capability Plan, which runs from 2025 to 2029.
Links to wider Five Eyes work
The Arcadia decision sits within wider Five Eyes technical cooperation. In June, the New Zealand Security Intelligence Service joined Five Eyes partners for a Joint Five Eyes Bulletin titled Safeguarding our Secrets NZSIS. That month the alliance warned that new AI models pose an urgent cyber risk Reuters.
Leaders of the Five Eyes cyber security agencies issued a call to action on AI preparedness to address cyber risk driven by Frontier AI, the most advanced AI systems. New Zealand signed up to a rare Five Eyes intelligence statement warning that powerful AI models are capable of taking down governments.
The broader context here is leverage and dependency. For a small defence force, joint development offers access to capabilities it cannot fund on its own, but the price is committing early before costs are firm. The briefings put that trade-off in plain terms. Interoperability is treated not as helpful but as the condition for continued access.
For Wellington, three questions now stand out. First, what share of the six-year build New Zealand will carry, and whether Budget 2027 can fit it in with the existing capability plan. Second, what the May memorandum locks in for governance, including how national control is kept in practice once systems and data standards come together. Third, whether Arcadia and the joint AI preparedness work join into a single information environment, where exclusion from one means reduced standing in the other.
