In public, former New Zealand Prime Minister David Lange was staunch in his anti-nuclear stance, but in private it was a different story, recently released CIA documents show.
The spy agency has uploaded 12 million declassified dossiers online, ranging from 1948 to the 1980s.
Among them are extensive official reports about New Zealand's nuclear-free stance and the strain it created on the relationship with the United States.
Mr Lange and Labour campaigned hard in 1984 on banning nuclear-powered ships and weaponry in New Zealand waters, which helped them storm to power that year.
But a document dated July 3, 1984 entitled 'New Zealand: Muldoon Goes to the Polls', claims Mr Lange's public statements differed from his private thoughts.
"Lange has privately assured US officials that he is personally satisfied that nuclear propulsion is safe and that his reservations are centred on nuclear weaponry," the briefing says.
It also claims senior Ministry of Foreign Affairs officials said "some sort of compromise" could be reached over future ship visits.
"We are not so sanguine."
Following New Zealand's nuclear-free declaration in 1984, it was noted then-US President Ronald Reagan considered their response to the policy was "appropriate" in showing New Zealand "cannot enjoy the benefits accorded a good ally without complying with the necessary responsibilities".
It says the US security obligations relating to New Zealand should be "maintained under review", and the country should be stripped of the "special relationship" status of a "very close ally" when it comes to foreign military sales.
A further dossier from 1985 says the stance is a "direct challenge" to its policy to neither confirm nor deny the presence of nuclear weapons on US ships or planes.
It describes their retaliation over the policy, and also lists the ramifications of the decision, including increasing Soviet incentives to "promote disunity" among US allies and to wait for successes by other anti-nuclear groups around the world, rather than commit to arms reduction.
"With great regret, the decision has been taken to curtail our military and other ANZUS-connected relationships with New Zealand until the government of New Zealand changes its policy," the document says.
Despite that, it still considered New Zealand a "friend", with the door still open to "the return of an old ally".
Australia not happy with non-nuclear stance either
New Zealand's trans-Tasman neighbours were also "dismayed" over the policy, saying it could "spell the end" of the ANZUS alliance and embolden the left wing of Australia's Labor Party.
In a 1985 briefing examining 'A Distancing Over Nuclear Issues' between the two countries, Labor Prime Minister Bob Hawke wanted to stay out of what it saw as a US-NZ problem.
"Canberra will consult with Washington, but will hold back from any approaches to Wellington that could be taken as interference.
"The New Zealanders are quick to see as patronising any attempt by their larger neighbour to discuss bilateral issues."
New Zealand's decision made waves in the Australian political world, with the anti-nuclear movement encouraging their trans-Tasman counterparts - "a development that has already cost Hawke politically," the document reads.
It notes the surprising popularity of the "hastily organised" Nuclear Disarmament Party in the Australian federal election in December 1984, which the CIA believed was a direct result of New Zealand's policy.
It also led to a number of anti-nuclear movements in several states.
The relationship between the US and New Zealand thawed last year, with warship USS Sampson arriving in New Zealand waters to celebrate the Navy's 75th anniversary - the first time a US ship has been allowed to visit the country.
US feared 'racial tensions' over Māori land claims
While there was concern about our anti-nuclear stance, the CIA also found Treaty of Waitangi claims troubling.
In the documents, the US Embassy notes there could be a long-term economic impact should land be given back to iwi, and that the Government would face backlash.
The October 25, 1988 document titled 'Racial Tensions: A Growing Factor in New Zealand Politics', it notes "growing political activism" by Māori which were "straining relations" with Pakeha.
"Although the risk of racial violence is small, tensions are likely to increase as the slumping economy swells unemployment among Māori, and as public sentiment builds against Māori demands."
It notes those tensions would make the upcoming 1990 election a difficult one for then Prime Minister David Lange and the Labour Party with an opportunity for National to capitalise on it.
"We believe… [Lange's] government will be hard-pressed to resolve Māori land claims without suffering a voter backlash from European New Zealanders."
The trove of documents also details Prime Minister Robert Muldoon's "domination" of the political scene in 1978 and his focus on reviving "New Zealand's seriously depressed economy" but with only "limited success".
It notes New Zealand has been "heavily dependent for years on US strategic protection, and Muldoon has stressed this dependence more than have his predecessors".
Mr Muldoon had also "eased the occasional strains that the ANZUS alliance suffered during the preceding Labour government".
The same document also details "unabashedly anti-Soviet" Mr Muldoon's efforts to stop the Soviet Union spread in the Pacific when they tried to set up ports in Tonga and Western Samoa.
In 1949, a document on the 'Communist influence in New Zealand' says the threat was "insignificant", noting the country's Communist Party was small in number and has "little overall influence".