Praised by conservative commentators as a straight-talker on foreign policy, but condemned by many as a war mongering hawk, John Bolton is one of President Trump's most unexpected and controversial recruits.
Amid reports he is bound for Australia in coming weeks, there is speculation surrounding what could be the purpose for his visit.
The staunch conservative served under Ronald Reagan, George HW Bush and George W Bush, and has developed a reputation for his often abrasive style of diplomacy and provocative statements. 
National security adviser John Bolton, accompanied by Secretary of State Mike Pompeo, and President Donald Trump. Source: AP
It emerged this week Mr Bolton is expected to travel to Australia off the back of US President Donald Trump’s upcoming
Last year, President Donald Trump appointed Mr Bolton as his national security advisor, replacing HR McMaster.
While his appointment came as a surprise to many, Mr Bolton has wasted no time in making the job his own.
"His way of doing the job is to go out and talk to folks directly, so he's making these headlining trips to Europe, he's talking to allies about Venezuela, and really trying to solidify his own relationships with these folks in order to get what he wants," Jared Mondschein, analyst at the United States Studies Centre told SBS News.
US President Donald Trump. Source: AAP
Some analysts fear the timing of the reported meeting could signal a shift in priorities for US foreign policy - former Australian diplomat and Vice-President of Australians for War Powers Reform Alison Broinowski believes that once the US eventually deems the threat from North Korea to be neutralised, it is only a matter of time before the focus shifts to Iran.
"John Bolton wants a war with Iran, and I don't think that Trump is fixed on that, but Bolton is," she said.
Mr Bolton's aggressive stance on Iran has been well publicised - in 2006, he threatened the country with "tangible and painful consequences".
Nine years later, in an op-ed for the New York Times, he argued for the need to "bomb Iran".
Earlier this week, he was sounding equally combative - as Iran marked the 40th anniversary of the Islamic Revolution, Mr Bolton took the opportunity to condemn Tehran as responsible for the suffering of Iranians and endangering the lives of people all over the world.
"For all your boasts, for all your threats to the life of the American President, you are responsible for terrorizing your own people," he said in a message to Iran's Supreme Leader.
Ms Broinowski is concerned Australia could be called in to support the US in a potential conflict with Iran - and she believes that could be a key reason for Mr Bolton's planned visit.
"What has always been important to American policy is for them to find allies who will support any move they want to make," she said.
However, others believe the reason for the visit may be much closer to home - and that Mr Bolton's primary intention would most likely be to challenge China's influence in the Asia-Pacific region.
"Across the left, and right, and even among the allies, there is a cohesion in terms of really trying to get China to address what have been longstanding complaints from the US and its allies," Mr Mondschein said.
