On an isolated block of defence land north of Darwin, a group of United States marines has spent the past week war-gaming their response to a fake embassy siege on the tropical Tiwi Islands.
With marines stationed at every US embassy around the world, the annual Exercise Darrandarra is crucial training on securing and evacuating US assets in foreign countries.
The exercise is held each year in a remote Northern Territory location as part of the annual six-month rotation of marines to the Top End.
While the drills on the Tiwis' Bathurst Island were a make-believe scenario, Master Gunnery Sergeant Robert Robinson said the marines were likely to be deployed in similar real-life operations throughout their careers.
"I think we probably do some type of a non-combatant evacuation maybe once a year," Sergeant Robinson said.
"We can always be called upon to do it and we never know when that's going to be, so we have to be prepared to do it."
Despite searing midday heat and unseasonally damp evenings, the marines were tested almost 24 hours a day for a week straight during the exercise.
At the gates of the "US Embassy Tiwi", marines role-played as local protesters, while others took on the role of local guards from the fictional host nation.
Machine gunners, medics and even a legitimate representative from Canberra's US Embassy took part in the training.
As the week drew on, the scenarios thrown at the young marines – with an average age of about 21– became more complicated.
What started as loud but non-violent protests along the "embassy" fence line were overtaken by suicide bombings and mass casualty events.
Suspicious packages and embassy intruders were thrown into the mix as well.
Each night, as the marines took a brief break, their commanders would sit down to dream up new challenges to throw at the young men and women.
"We have a bit of fun with it … we start off very small and then build up and build up and then it gets to the worst-case scenario," Lieutenant Tess Miller explained.
"We kill off their leadership or take away [communications] and then they have to deal with it."
Sergeant Robinson said the main test for the young marines on the ground was making sure they kept their cool.
"What we want to do is poke them and prod them over a couple of days and see if we [can] get under their skin," he said.
Sergeant Jacob Sullivan, who oversaw a team of machine gunners during the exercise, said security and evacuation operations required marines to have a different mindset than they would in a typical combat situation.
"If a guy is banging a stick … at the fence, I had one marine ask me 'do we engage?'," Sergeant Sullivan said.
"And [the answer is] 'no' because he's behind a fence, he's a civilian and you're trying to compare a rifle to a stick.
"You have to think about the force you're using and the force they're using."
US training a signal of things to come
The training is an annual component of the Marine Rotational Force-Darwin (MRF-D), the six-month training deployment borne out of a deal between the US and Australia now in its 11th year.
In 2022, the marines who took part were the most capable and combat-ready group ever deployed.
"With Fifth Marine Regiment [which makes up the MRF-D] already being a standing regiment, we were able to fall in on this mission as already combat-credible," Sergeant Robinson said.
"We are prepared to continue to train here with the Australians and our other partners in the region and also we are prepared to respond to crisis anywhere in the Pacific region."
As tensions in the Indo-Pacific region continue to simmer, one expert said the step-up in experience of the marines now based in northern Australia was a subtle but significant shift.
The Australian Strategic Policy Institute's Dr John Coyne said the increased US presence in northern Australia signalled the region's strategic importance to both countries.
"There's clear evidence the US government is going to invest more in ensuring that supply chains [and] defence logistics facilities are present in northern Australia and ready to support a range of contingencies," he said.
Around 2,000 marines are based in the Top End this dry season as part of the 2022 rotation.
Only 200 marines were deployed in 2012. Dr Coyne expects the number to keep increasing.
"Forward deployment in Darwin and northern Australia really provides proximity to the region, it provides a capacity [for the US] to leapfrog operations," Dr Coyne said.
"It provides the US military with a forward operating base from which it can launch into the region."
But Dr Coyne said he believes the US would stop short of establishing a formal, permanent American military base in the NT.
"There will be increased ship visits and increased force visits in the coming years," he said.
"I think the concept of bases as we understood them in the Cold War — very few governments are welcoming of a more formal US-basing arrangement."
As for whether an increased US footprint in Darwin makes northern Australia a target for conflict, Dr Coyne said he believed the presence of American forces was actually a deterrent.
