It has been the most tightly held secret in Australian political, defence and scientific circles for more than 18 months.
Australia was taking an interest in signing a historic strategic agreement with the US and UK, with nuclear-powered submarines a key element of the deal.
The federal government had signed up in 2016 to working with France's Naval Group to build 12 conventional-powered submarines to replace the ageing Collins-class fleet.
At the time, there was no thought of adopting any nuclear technology, and in any case it was not being offered to Australia.
Much work has since been put into the $90 billion Attack-class project in Australia and France, with $2.4 billion spent to date.
Australia's Defence Strategic Update released in July last year committed to the Attack-class project.
However, what was more significant in the update was what it said about strategic change in the Indo-Pacific region.
"Our region is in the midst of the most consequential strategic realignment since the Second World War, and trends including military modernisation, technological disruption and the risk of state-on-state conflict are further complicating our nation's strategic circumstances," it said.
"The Indo-Pacific is at the centre of greater strategic competition, making the region more contested and apprehensive. These trends are continuing and will potentially sharpen as a result of the coronavirus (COVID-19) pandemic."
Since then, top brass in the Australian military believe there has been an accelerated pace of change and complexity in this strategic realignment, including China's active pursuit of greater influence.
This required a refreshed approach to old allies, a change in thought on submarines and the acquisition of a new range of weapons and technologies.
What were known as "systems-level" talks were quietly launched, involving top people in defence, science and technology.
Politicians were largely kept out of these discussions and there was no engagement with then US president Donald Trump.
But by April this year the idea of a pact with the US and UK, and the potential use of nuclear technology, was elevated to the political sphere and taken up with Mr Trump's successor Joe Biden.
In June, Mr Morrison met in Cornwall on the sidelines of the G7 summit to discuss the AUKMIN agreement, the prime forum for the discussion of high-level policy between Australia and the United Kingdom.
At that meeting, he said, there was a "clear sense of shared purpose and an easy sense of agreement".
They looked each other in the eyes and said, 'Let's do it'.
Mr Morrison later in the European trip had dinner with French President Emmanuel Macron, where the prime minister outlined Australia's new strategic thinking.
He made it known there were "very real issues" with the ability of the Attack class to meet these new needs.
The French partnership continued in good faith until the US formally made it known to Australia it would definitely share its nuclear submarine technology, for only the second time since 1958 when the UK was the beneficiary.
The final decision on the new partnership and the submarines was made known in a joint statement from the two prime ministers and Mr Biden on Thursday.
Australian Associated Press