As China and the United States play geopolitical tug-of-war on the global stage, it's feeling a little too close for comfort in one pocket of Australia.

US Marines will reach their full complement of 2,500 troops training in Darwin by July, which will correspond with a boost of $250 million for capital works to improve Australian Defence Force facilities in the Top End.

Meanwhile Landbridge, a Chinese company with ties to that government, leased the Darwin port for almost a century, provoking an international flurry of consternation and a rebuke from former US president Barack Obama.

As things heat up, a number of you have asked the ABC what this posturing of super powers in the Asia-Pacific region means for Australia, caught in the middle.

"Is there an increased risk of war in our region and what does that mean for Darwin?" wondered Annette.

"How much more likely is an attack on Darwin compared to other Australian capitals?" mused questioner Ethel.

Would the US presence in the NT continue and grow? several people asked.

Curious Darwin is our story series where you ask us the questions, vote for your favourite, and we investigate. You can submit your questions on any topic at all, or vote on our next investigation.

The US sends marines to the NT every year for training rotations. ( Facebook: Marine Rotational Force Darwin )

The world zooms in

Australia's Top End is an important pivotal place for a range of national security and foreign affairs issues, said John Coyne, from the Australian Strategic Policy Institute.

"Darwin is critical … because it's our northern centre, the base from which we can defend our approaches, and from which we have our linkages into the region," he said.

Mr Coyne said that during the Cold War in the mid-80s, the last time Australia planned and talked in depth about defence, the world was a very different place.

"We were a long way away from the power conflicts; America and Russia were the great powers who were in conflict," he said.

"The region was relatively stable, Australia had a technological edge in terms of its weapons and planning distances … and there was this assessment that there would be more than 10 years' warning if there was going to be a conflict in the region."

Fast forward to 2019, and Australia is no longer a long way away from great powers in competition, with China and the US jostling, the US and Russia at odds, and tensions rising over the South China Sea as China extends its political and diplomatic power across the region.

US President Donald Trump and Chinese President Xi Jinping have had an up-and-down relationship. ( Reuters: Carlos Barri )

"There's an increasing shortfall in food proteins, so there's much more aggressive fishing tactics going on in terms of the Chinese fishing fleets," Mr Coyne said.

"We no longer have a technological edge in terms of weapons in the region, there are people who have got better weapons than us, and more of them [with long ballistic ranges].

"We no longer have the luxury of more than 10 years' notice for the possibility of conflict, it's likely to be significantly less than that."

Caught between giants

The presence of US Marines in northern Australia and the building of resilience in the Top End community has become more important than ever before, Mr Coyne said.

"[The US and China] are posturing, which is important to do, to avoid conflict by being able to show that each has made a commitment," he said.

Alexey Muraviev, head of Curtin University's International Relations and National Security programs, agrees.

"The US presence in the NT is a signal to the region that the US intends to position its forces across key locations in order to respond to current and emergent threats," he said.

"I don't think [their presence] is a threat to China.

"I don't think 2,500 or so US Marines would really [cause] the Chinese to lose their sleep in the middle of the night, but it's not the numbers that really matter, it's the symbolism that comes with it."

Most of the diplomatic manoeuvring taking place between the US and China was focused on preventing a conflict from breaking out, said Neil James, executive director of the Australia Defence Association.

"A bit of effort spent trying to shape the international situation and trying to deter a war from starting is always better in economic, humanitarian, and moral terms than having to fight a war," he said.

Sorry, this video has expired Concerns of a "cold war confrontation" between the US and China is brewing, according to one expert (ABC News: Jarrod Fankhauser)

Who is Australia?

Located in the Asia-Pacific but with historically strong ties to the US and Europe, Australia has struggled to articulate who it is as a nation, Dr Muraviev said.

"We have declared time and time again that we're in the Asia-Pacific community … the question we tend to avoid critically addressing is whether the region considers us to be a part of them… [because] we haven't really diverted ourselves away from the Anglo-Saxon sphere," he said.

"A lot of our thinking and planning suffers from us standing at those crossroads while we're trying to retain our historical ties and sense how it can fit in this new change in reality."

He said that Australia was currently trying to have it both ways, by declaring that the US was the number one political, military and strategic priority, while maintaining that China was critical to economic wellbeing as Australia's largest trading partner.

"However, we have political and strategic concerns about China's current behaviours, about its strategic intent and what it's placed to do as the rising regional power that aspires to acquire global superpower status in the foreseeable future," Dr Muraviev said.

"Sooner or later the Australian political establishment will have to exercise a degree of political courage to determine where our strategic future is.

"Certainly the upgrade of our defence capability and investment that goes in building up key military infrastructure, including in the NT, is very much driven by our growing awareness that China is on the rise… and China may be threatening our interests in the medium to long-term future."

Australian troops march through Darwin on ANZAC Day. ( Facebook: Marine Rotational Force Darwin )

A hypothetical war?

So how much of a risk is Australia and, by extension, the NT, facing as a result of its ties to the US?

All three experts agree that there is a small risk, but it's balanced by other factors.

"Unfortunately in the three generations since the end of World War II, many Australians have grown quite complacent [about peacetime] and we just assume that it's always going to be like this," Mr James said.

"Well, there's a risk that it won't always be like this, because one major power in the world — because it's not accountably and democratically governed — wants to change things from the way the UN charter was developed to resolve disputes by negotiation and peaceful discussion."

China is Australia's biggest trading partner but is also making moves in the region that have authorities uncomfortable. ( Reuters )

Dr Muraviev pointed out that by having alliances, Australia is forced to choose sides, and as a result, joint defence facilities would be treated as legitimate military targets.

"In terms of people feeling concern about us being targets, we need to do a reality check," he said.

"If we're committed to a particular military alliance … we have to understand the benefits this alliance gives us — we have the nuclear umbrella provided by the US, we still count on them as our principal security partner — and it comes with sets of responsibilities and a set of risks."

Australia has committed in a bipartisan agreement to spend 2 per cent of its gross domestic product each year on defence, "an insurance policy" it hopes never to have to cash in, Dr Coyne said.

These days, no part of Australia now is immune to a hypothetical strike by a military power, he said, and Russia and China would be able to hit targets well south of Darwin should a conflict break out.

"There are other facilities in Australia's north that are critical to Australia's defence, like Pine Gap, the Joint Over the Horizon Radar Network, the RAAF base at Tindal; these are really important critical infrastructure and capabilities to Australia's defence," Dr Coyne said.

"They're our eyes, ears, and indeed our own strategic strike capabilities, so it is quite possible that those would be targeted."

With Australia's huge coastline — almost 26,000km long — the nation would struggle to defend a full-scale amphibious assault.

"Even in times of mobilisation, I think our capacity to respond to a full-scale invasion may be limited to a couple of strategic zones, but we won't be able to defend the entire north-western approach of Australia," Dr Muraviev said.

The last time Darwin was attacked was by the Japanese during World War Two. ( Northern Territory Library )

On the plus side, although an invasion of Australia wouldn't be difficult to achieve, he said an occupation would be far more difficult to sustain.

"It's a massive country, major parts of which are not suitable for comfortable living conditions, there's obviously going to be a degree of resistance … It would require an enormous commitment of human resources, et cetera, so it wouldn't be worth it," he said.

Given that so much of how Australians interact with the outside world takes place online, cyberspace is likely to be the domain of a hypothetical attack.

"A country is not necessarily going to assert itself using mechanisms other than war … it doesn't necessarily need to blow things up to deny you the opportunity to use them," Dr Coyne said.

As Dr Muraviev noted: "In order to disable us, all the enemy needs to do is paralyse our ability to interact with the outside world by destroying ports, airports, and inflicting significant damage on our defence and communications, and then Australia would find itself in a state of crisis."

Threats to water, food, fuel security

So although an attack is unlikely to come in the form of a physical invasion, Australia is vulnerable in other ways.

Dr Coyne said there needed to be an investment in what he termed "resilience" in the Top End, such as boosting water, food, and fuel supplies.

"At the moment the water basin is dropping, and there's a single point of failure in the provision of fresh drinking water in Darwin; that's a concern," he said.

"Fuel supply's another: there aren't bulk fuel storage facilities that would allow the NT and Darwin to continue operating for 100 days, it's more like seven days they've got, so that needs further investment."

Dr Coyne said that having a robust local economy and community in the NT was critical to Australia's longer term national security.

"Defence needs to draw upon the infrastructure and the local economy, everything from maintenance, ship lifts, and communities that can pull together in times of crisis," he said.

"At the moment where you've got shopfronts closing, strong economic challenges, those need to be addressed to create that thriving economy and community that will be able to withstand sudden shocks."