US President Donald Trump's pick to fill the role of acting secretary of defense after the sudden departure of General James Mattis is no stranger to Australia.
Patrick Shanahan, a former Boeing executive and Mattis' deputy at the Pentagon since April last year, regularly talks up the "robust defence relationship" the US and Australia shares and "the common strategic challenges" the longtime allies face.
In February, when then prime minister Malcolm Turnbull visited Washington DC, Mr Shanahan was waiting on the front steps of the Pentagon to greet him and in April, Mr Shanahan hosted Australian Defence Industry Minister Christopher Pyne.
It was General Mattis' concerns about Mr Trump's treatment of allies, the president's surprise plan to pull US troops out of Syria and the belief Mr Trump should replace him with someone "whose views are better aligned with yours" that led to the general's resignation last week.
General Mattis had planned to leave the Pentagon at the end of February but Mr Trump, reportedly stung by the tone of the general's resignation letter, announced on Sunday via Twitter Mr Shanahan would start in the top job on January 1 and his boss' departure would be fast-tracked.
There were concerns General Mattis' departure would shake up the US-Australian military alliance but Mr Shanahan, 56, has been a visible and positive presence at numerous public events involving the two nations.
Mr Shanahan, during his meeting with Mr Turnbull in February, highlighted America's "commitment to the Indo-Pacific region, and to our allies and partners", according to the Pentagon's readout.
At a service at the National Cathedral in Washington DC in June, Mr Shanahan spoke about the 100 Years of Mateship shared by US and Australian forces since the World War I Battle of Hamel in northern France.
"Its walls were not made of stone or wood, but of flesh and blood," he said.
"Its mortar was the mud of the trenches.
"Its foundation was the courage in young kids from Queens and Queensland, from Adelaide to Appalachia."
