Patrick Shanahan (Picture: US Department of Defense).
Until a few days ago, the name Patrick Shanahan probably meant little to most people.
He was second-in-line at the US Department of Defense but kept a low profile in the job.
However, the spectacular falling-out between the outgoing Secretary General James Mattis and President Donald Trump, has thrust him into the limelight.
Mr Shanahan, like many in the Trump government, is a businessman.
He spent 30 years at defence and commercial aviation giant, Boeing, playing a key role in the development of the 787 Dreamliner. He finished at the company as senior vice president of their supply chain.
In a statement, Mr Shanahan said: "Under the direction of President Trump, the Department of Defense remains focused on safeguarding our nation.
"We have deep respect for Secretary Mattis’ lifetime of service, and it has been a privilege to serve as his deputy secretary.
"As acting secretary of defense, I now look forward to working with President Trump to carry out his vision alongside strong leaders including the service secretaries, the Joint Chiefs of Staff, the combatant commanders, and senior personnel in the Office of the Secretary of Defense."
In a tweet, President Trump announced Mr Shanahan's promotion and praised his "long list of accomplishments".
Mr Shanahan will become the 33rd US Secretary of Defense after General Mattis resigned over President Trump's controversial decision to withdraw US troops from Syria.
In his resignation letter, he said his move would allow the President to find a “Secretary of Defense whose views are better aligned with yours".
General Mattis said his February departure date was designed to minimise disruption to the department but that was brought forward to 1 January by President Trump.
But what does all this mean for the new man?
A steep learning curve, think many.
Aside from his year as Deputy Secretary of Defense, he has little experience in the world of government, international relationship building and defence engagement with partner nations.
Rather it’s thought he’s a man for detail and process - his supply-chain work with Boeing would seem to show that.
It’s reported he’s spent the last year inside the Pentagon reshaping areas like IT and introducing business-style measurement metrics to the organisation. Essentially, bringing business to the heart of defence.
All very different in style and outcome to his predecessor, who was a military man through-and-through.
However, Mr Shanahan does have military roots. His father served in Vietnam, being awarded the Bronze Star.
How long this job remains his is anyone’s guess.
He is in the role in an acting capacity. President Trump’s necessity of removing General Mattis quickly perhaps made him the only choice.
If the job is to become his permanently, it is likely to depend on whether he can fully support what the President wants. For those whose opinions differ, they tend to move on quickly.