US President Donald Trump has named Lieutenant General Herbert Raymond McMaster as his national security adviser, taking over the post left vacant after Michael Flynn's resignation.
"He is the man of tremendous talent and tremendous experience," Trump told reporters on Monday, sitting next to McMaster, 54, who was dressed in uniform.
"He is highly respected by everybody in the military and we are very honoured to have him," Trump said from West Palm Beach, Florida.
Trump also named Keith Kellogg, a retired army general who has been serving as the acting national security adviser, as chief of staff to the National Security Council.
The US president said John Bolton, a former ambassador to the United Nations, would serve the administration in another capacity.
Trump, McMaster and Kellogg ignored questions from reporters after the announcement, including over whether the new national security adviser would be allowed to hire his own staff.
The appointment came a week after Flynn was asked to quit after reports emerged that the retired lieutenant general misled Vice President Mike Pence about having spoken to Russia's ambassador about US sanctions before Trump's inauguration.
Trump interviewed four finalists to replace Flynn on Sunday, according to White House spokeswoman Sarah Sanders.
Robert Harward, a retired vice admiral and former Navy SEAL, reportedly turned down Trump's offer of the job last week over concerns that he would not be able to bring in his own team to staff the National Security Council.
Other reports said he was put off by apparent chaos in the White House.
A serving soldier
The national security adviser is an independent aide to the president and does not require confirmation by the US Senate. The role has varied from administration to administration, but the adviser attends National Security Council meetings along with the heads of the state department, the department of defence and key security agencies.
Having served in Iraq and Afghanistan, McMaster is a highly regarded military tactician known as "HR".
In 2014, he was listed as one of Time magazine's 100 most influential people, partly because of his willingness to buck the system.
Al Jazeera's James Bays, reporting from Washington, DC, said that since McMaster was a serving soldier, he could not turn the president down even if he wanted to.
McMaster is "certainly seen as one of the thinkers of the US military", Bays said.
McMaster's fame grew after his 1997 book Dereliction of Duty criticised the country's military and political leadership for poor leadership during the Vietnam War.
"The main theme of that book was that during the time of Vietnam the generals didn’t say enough; they didn’t speak up enough to the president," Bays said.
"A very interesting theme as this is the man who is now going to be guiding and advising the president on national security matters."
McMaster heads the Army Capabilities and Integration Centre and is deputy commanding general of the Futures Centre at US Army Training and Doctrine Command at Fort Eustis.
Source: Al Jazeera and news agencies