

President Donald Trump announced on Monday that he asked Lieutenant General Herbert Raymond "H.R." McMaster to serve as his national security adviser, one week after Michael Flynn was forced to resign from the post.



McMaster, 54, is a career Army officer who served in the Persian Gulf War and wars in Afghanistan and Iraq as well.

Trump also announced at his Mar-a-Lago estate in Palm Beach, Florida on Monday that Keith Kellogg, who had been serving as acting National Security Adviser in Flynn's absence, would become chief of staff for the National Security Council.

13 PHOTOS Army Lt. Gen. H.R. McMaster See Gallery Army Lt. Gen. H.R. McMaster Newly named National Security Adviser Army Lt. Gen. H.R. McMaster listens as U.S. President Donald Trump makes the announcement at his Mar-a-Lago estate in Palm Beach, Florida U.S. February 20, 2017. REUTERS/Kevin Lamarque U.S. President Donald Trump announces his new National Security Adviser Army Lt. Gen. H.R. McMaster (L) at his Mar-a-Lago estate in Palm Beach, Florida U.S. February 20, 2017. REUTERS/Kevin Lamarque Newly appointed National Security Adviser Army Lt. Gen. H.R. McMaster listens as U.S. President Donald Trump makes the announcement at his Mar-a-Lago estate in Palm Beach, Florida U.S. February 20, 2017. REUTERS/Kevin Lamarque U.S. President Donald Trump shakes hands with his new National Security Adviser Army Lt. Gen. H.R. McMaster after making the announcement at his Mar-a-Lago estate in Palm Beach, Florida U.S. February 20, 2017. REUTERS/Kevin Lamarque TPX IMAGES OF THE DAY U.S. President Donald Trump departs the room after announcing his new National Security Adviser Lt. Gen. H.R. McMaster (L) who receives a handshake from newly named chief of staff of the National Security Council Gen. Keith Kellogg (C) at Trump's Mar-a-Lago estate in Palm Beach, Florida U.S. February 20, 2017. REUTERS/Kevin Lamarque U.S. President Donald Trump shakes hands with his new National Security Adviser Army Lt. Gen. H.R. McMaster after making the announcement at his Mar-a-Lago estate in Palm Beach, Florida U.S. February 20, 2017. REUTERS/Kevin Lamarque White House National Security Advisor H.R. McMaster (C) and Chief Strategist Steve Bannon (L) attend a joint news conference between U.S. President Donald Trump and NATO Secretary General Jens Stoltenberg in the Oval Office at the White House in Washington, U.S., April 12, 2017. REUTERS/Carlos Barria White House National Security Advisor H.R. McMaster delivers a statement to reporters at the White House in Washington, U.S. May 15, 2017. REUTERS/Jonathan Ernst White House national security advisor H.R. McMaster (L) arrives with Press Secretary Sean Spicer (R) to speak to reporters in the White House briefing room in Washington, U.S., May 16, 2017. REUTERS/Joshua Roberts White House senior advisor Jared Kushner (2nd R) looks on as Lockheed Martin Chairman and CEO Marillyn Hewson (L) exchanges agreements with a Saudi official after a signing ceremony between Saudi Arabia's King Salman bin Abdulaziz Al Saud and U.S. President Donald Trump at the Royal Court in Riyadh, Saudi Arabia May 20, 2017. Also pictured are White House national security advisor H.R. McMaster (L), chief economic advisor Gary Cohn (3rd R) and Chief of Staff Reince Priebus (R). REUTERS/Jonathan Ernst U.S. President Donald Trump walks to Marine One with National Security Advisor H.R. McMaster as they depart for a day trip to Miami from the White House in Washington, U.S., June 16, 2017. REUTERS/Joshua Roberts U.S. President Donald Trump eats Belgian chocolate flanked by Secretary of State Rex Tillerson (L) and National security adviser H.R. McMaster react as they eat Belgian chocolate during their meeting with Belgian Prime Minister Charles Michel in Brussels, Belgium, May 24, 2017. REUTERS/Jonathan Ernst White House National Security Advisor H.R. McMaster joins White House Press Secretary Sarah Huckabee Sanders (unseen) for the daily briefing, to address sanctions on Venezuelan President Nicolas Maduro , at the White House in Washington, U.S. July 31, 2017. REUTERS/Jonathan Ernst Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

Trump said that he will ask John Bolton, who had also been on his short list of candidates for Flynn's replacement, to serve another role.

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 replaces a Trump loyalist. Michael Flynn, a retired Army lieutenant general, was fired 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.

The ouster, 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.

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

9 PHOTOS Reaction to Michael Flynn's resignation See Gallery Reaction to Michael Flynn's resignation Michael Flynn has resigned as Trump's national security adviser. KEEP SHOWING UP. Our resistance is working! #WhyIResist Im sad #MichaelFlynn resigned but at the end President Trump did what he had to do and thats says everything. Flynn's resignation CANNOT be end of the story. Who talked to who? When? Who knew? When? How far up did it go? How much of dossier true? Well, not even a month in and the first resignation due to scandal, and I doubt it'll be the last.#MICHAELFLYNN #Flynngate doesn't bode well for @seanspicer. At all. https://t.co/czu8yerodG If @POTUS knew of #MichaelFlynn and #Russia, then we are a country in crisis now. Brian Williams goes there: "What did [Trump] know and when did he know it?" #flynn Dear Mike Flynn & Mike Flynn Jr., What goes around COMETS around. And given your pizza obsession... https://t.co/rmyO7wyJKX xo Philippe However welcomed General Flynn's resignation is, remember that President Trump's Russia connections and intentions… https://t.co/Trc2oMXDor Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

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 Defense and key security agencies.

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 coordinates, in what many consider the biggest tank battle since World War Two.

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.

(Reporting by AOL with additional reporting by Reuters)