A large military exercise involving Australian and US troops is underway in the West Kimberley for the first time.
Exercise Koolendong occurs annually in the Northern Territory but this year is also operating out of Yampi Sound Training Area and RAAF Base Curtin, both near Derby.
More than 2,200 marines, soldiers and airwing are testing their ability to outwit a fictional enemy nicknamed Murphy 22 across rugged terrain in the Kimberley and NT.
"One of the key components … is being able to train as you would fight," Captain Joe DiPietro, of the US Marine Rotational Force, said.
"Having a thinking enemy that can move and can build defensive positions or move into different ambush areas and being able to combat that is a critical component of Koolendong 22."
But an unexpected challenge has been the unseasonably cold nights, with temperatures at Yampi Sound dropping below 4 degrees Celsius regularly this month.
"We all got [to Darwin] around February-March when it was extremely hot and humid. So the transition from that to what they're operating in right now has been a big change."
Moving equipment without roads and communicating in areas far beyond mobile phone reception was also part of the test.
"There's a lot of logistics challenges that we face. But we have a really good team here," Captain DiPietro said.
"The Australians, both in defence and civilian, have been able to help us with civilian barges, shipping, military, shipping aircraft, so utilising different resources and different assets to get across those wide ranges is a key part of this exercise."