The United States is preparing to deploy up to six nuclear-capable B-52 bombers to northern Australia, a provocative move experts say is aimed squarely at China.
An investigation by Four Corners can reveal Washington is planning to build dedicated facilities for the giant aircraft at Tindal air base, south of Darwin.
Becca Wasser from the Centre for New American Security says putting B-52s in northern Australia is a warning to China, as fears grow Beijing is preparing for an assault on Taiwan.
"Having bombers that could range and potentially attack mainland China could be very important in sending a signal to China that any of its actions over Taiwan could also expand further," she says.
China's growing confidence about Taiwan invasion
In recent months, US war planners and analysts have brought forward estimates of when Beijing may look to take Taiwan.
"The time frame for an assault on Taiwan, I would put it at 2025 to 2027," says defence academic Oriana Skylar Mastro from Stanford University.
"This is largely dependent on when I think the Chinese leadership and in particular [President] Xi Jinping can be confident that his military can do this."
She says there is a growing confidence within the People's Liberation Army that it could successfully invade Taiwan.
"For 15 years I would ask the Chinese military if they could do this [invade Taiwan], and the answer was 'no'. So the fact that for the first time at the end of 2020 they're starting to say 'yes', I think that's a significant message we should pay attention to," she says.
Spy base expands
While both governments have signalled the growing US military presence in Australia, the expansion of one site is veiled in secrecy. There has been very little said about Pine Gap.
The joint US and Australian spy base near Alice Springs is undergoing a major upgrade, according to Richard Tanter.
He's spent months poring over satellite images of Pine Gap and estimates the number of giant antennas has grown by more than a third over the past seven years.
"This is at a time when the Australian Parliament has been informed of none of this, no statements by ministers no questions by politicians," he says.
Mr Tanter says Pine Gap's powerful "ears and eyes" are now heavily focused on China.
"The searching for Chinese missile sites, the searching for Chinese command sites, in a preparatory way, is absolutely on high priority at Pine Gap now," he says.
"This indicates the extraordinary importance and the increasing importance to the US at a time of potential war with China."
If a conflict broke out between the US and China, Mr Tanter says Pine Gap would play a hugely significant role, particularly around missile defence systems.
"Pine Gap would be detecting the launch of the missile … it would be queuing US missile defence systems to find that missile in mid-flight and attack it with their own missiles," he says.
Pine Gap's geo-location technology would then be used to find and destroy the missile launch site.
Paul Dibb, who held a high-level security clearance at Pine Gap for 30 years, says "it is the most potent intelligence collection facility that America has" outside of the US.
Mr Dibb says this put Pine Gap on targeting lists for the former Soviet Union during the Cold War, and it would be on those same lists for China in any conflict with the US.
"If it looked as though that crisis was going nuclear, China may want to take out Pine Gap as being the ears and eyes of America's capability," he says.