U.S. President Donald Trump said on Monday that Lt.-Gen. Herbert Raymond McMaster would be his new national security adviser, replacing Michael Flynn, again turning to the U.S. military to play a central role on his foreign policy team.

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. Speaking to reporters in West Palm Beach, Fla., where he spent the weekend, Trump said John Bolton, a former U.S. ambassador to the United Nations, would serve the administration in another capacity.

McMaster is a highly regarded military tactician and strategic thinker, but his selection surprised some observers who wondered how McMaster, who is known for questioning authority, would deal with a White House that has not welcomed criticism.

He is highly respected by everybody in the military and we're very honoured to have him," Trump said. "He's a man of tremendous talent and tremendous experience."

One subject on which Trump and McMaster could soon differ is Russia. McMaster shares the consensus view among the U.S. national security establishment that Russia is a threat and an antagonist to the United States, while McMaster's predecessor appeared to view it more as a potential geopolitical partner.

McMaster replaces a Trump loyalist. Flynn, a retired army lieutenant-general, was ousted as national security adviser on Feb. 13 after reports emerged that he had misled Vice-President Mike Pence about speaking to Russia's ambassador about U.S. sanctions before Trump's inauguration.

Flynn's departure, coming so early in Trump's administration, was another upset for a White House that has been hit by miscues, including the controversial rollout of a travel ban on people from seven Muslim-majority countries, since the Republican president took office on Jan. 20.

Senator John McCain, chairman of the Senate armed services committee and a frequent Trump critic, praised McMaster as an "outstanding" choice.

"I give President Trump great credit for this decision," McCain said in a statement.

Trump spent the weekend considering his options for replacing Flynn. His first choice, retired vice-admiral Robert Harward, turned down the job last week.

The national security adviser is an independent aide to the president and does not require confirmation by the U.S. 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.

A combat veteran

McMaster, 54, is a West Point graduate known as "H.R.," with a PhD in U.S. history from the University of North Carolina at Chapel Hill. He was listed as one of Time magazine's 100 most influential people in 2014, partly because of his willingness to buck the system.

A combat veteran, he gained renown in the first Gulf War — and was awarded a Silver Star — after he commanded a small troop of the U.S. 2nd Army Cavalry Regiment that destroyed a much larger Iraqi Republican Guard force in 1991 in a place called 73 Easting, for its map co-ordinates, in what many consider the biggest tank battle since the Second World War.

As one fellow officer put it, referring to Trump's inner circle of aides and speaking on condition of anonymity, the Trump White House "has its own Republican Guard, which may be harder for him to deal with than the Iraqis were." The Iraqi Republican Guard was ousted dictator Saddam Hussein's elite military force.

McMaster's fame grew after his 1997 book Dereliction of Duty criticized the country's military and political leadership for poor leadership during the Vietnam War.