Retired Lieutenant General Joseph Keith Kellogg Jr. has been chosen as acting National Security Advisor (NSA) to US President Donald Trump after the sudden resignation of Michael Flynn.
The role of NSA was created at the start of the Cold War as an in-house adviser to the President on high-level national security issues.
High-profile figures such as Henry Kissinger and Condoleezza Rice have taken the role in previous years.
But what do we know about the 26th person to hold this highly influential position?
72-year-old Kellogg campaigned for President Trump during his election campaign.
He served in the US Army for 36 years, travelling to Vietnam twice.
Before becaming Commander of 82nd Airborne Division in 1997, he was Director of the Command, Control, Communications, and Computers Directorate under the Joint Chiefs of Staff.
As the director of operations at the Coalition Provisional Authority, Kellogg played a key role in the 2003 Iraq War.
In an interview in 2003 with the Los Angeles Times he said:
"I'm the guy who's supposed to make the trains run on time."
This stands in contrast with Donald Trump's repeated statements that the war was a "total disaster".
Kellogg's wife Paige also served in the US Army and is a former Fort Bragg paratrooper and a veteran of the 1983 Grenada invasion.
Kellogg became a chief advisor to then Presidential candidate Donald Trump in 2016.
After Trump became President-elect Kellogg was appointed Head of the National Security Council.
He said in a statement at the time:
"I am honoured to not only be a part of this historic administration but also to be serving with [Lieutenant] General Flynn and KT McFarland, who are widely respected as some of the most experienced and strategic national security minds.”
Kellogg appointment as NSA is likely only temporary, with names such as disgraced former CIA director David Petraeus being tipped to fill the role as a permanent replacement for Michael Flynn.