The latest contingent of US Marines are leaving the Northern Territory after a rotation that, for the first time, included combined training with Australian forces in responding to natural disasters.
About 300 marines flew out of Darwin's RAAF base today, the first of the 1,250-strong contingent to depart after six months in the Top End.
Their departure marks the end of the sixth rotation of American troops to the NT under a deal struck in 2011 as part of a US military "pivot" to the Asia-Pacific region.
Deputy commander of Australia's Northern Command Captain Bryan Parker said the joint training helped the US and Australian forces work better together.
"The very fragile and rapidly changing international security environment that we find ourselves facing at the moment just reinforces how important it is to have a strong understanding at the tactical level," he said.
"We become familiar with each others techniques, tactics and procedures and [then] we can really work out how we can best utilise our respective forces, how we interoperate with each other and indeed how we cooperate to create a cogent capability so that collectively we can work together to assist in providing peace and security for the Indo-Pacific region."
Marine numbers were initially expected to reach 2,500 by 2017 but so far, have not risen above 1,250.
Since arriving in April, the marine force took part in 12 exercises with their Australian counterparts and also worked with armed forces from China, Indonesia, Malaysia, Singapore, Thailand and Vietnam.
US and Australian units also practised a joint response in a simulated natural disaster situation on South Goulburn Island off the Northern Territory coast for the first time.
US Lieutenant Colonel Brian Middleton said it made sense for the two forces to practice a combined relief effort.
"Both the ADF and the marines in those situations provide logistics capability, ability to bring in supplies that are needed [and the] ability to supply manpower and muscle as well," he said.
US and Australian units also practised a joint response in a natural disaster situation.
The Australian Defence department said details for next year's rotation and beyond were subject to discussions between the Australian and US Governments.
