Who is HR McMaster, Trump's new national security adviser?
Donald Trump's new national security advisor has been appointed in the shadow of a controversy after his predecessor lasted just three weeks in the job.
The choice has been well-received by both analysts and politicians - even some, like Senator John McCain, who have been critical of many of President Trump's decisions.
But who is Herbert Raymond McMaster?
A student of history
Lieutenant General HR McMaster is a decorated military official, having served in command positions during the Gulf War in the early 1990s and with the Central Command during the Iraq war in the early 2000s.
He was awarded the silver star for valour for his actions. In Afghanistan, he headed an anti-corruption and transparency task force.
But he is also known for his academic interest in history - and applying that intellectual approach to the battlefield.
Lt Gen McMaster graduated from the United States Military Academy in 1984, but went on to become something of a scholar of military history.
He earned an MA in history from the University of North Carolina in 1994, and taught history at the military academy for two years, before being awarded a PhD in American history in 1996.
That same year, he published a popular military history of the Vietnam War, "Dereliction of Duty", which was deeply critical of the decision-making process in Washington during the era.
The New York Times review of the book credited Lt Gen McMaster as having "doggedly waded through the records of every meeting of the Joint Chiefs" and noted that he concluded that the war was ''lost in Washington . . . even before the first American units were deployed".
That academic mindset and intellectual approach to military command impressed many people during this time in Iraq and Afghanistan.
He is widely labelled as a deep military thinker: Time magazine said that he "might be the 21st Century Army's pre-eminent warrior-thinker".
In 2005, he led an operation at Tal Afar in Iraq which was widely held as an example of success in a difficult war.
He seized the town, cutting it off from outside fighters - and then slowly but surely worked his way through the city districts, leaving troop outposts in place - and not allowing the enemy to return, in stark contrast to earlier US strategy.
Lt Gen McMaster's approach was lauded by President George W Bush and Secretary of State Condoleezza Rice.
Writing at the time for the Daily Telegraph, Tim Collins, a former SAS officer and journalist, said Lt Gen McMaster - then a colonel - had taken "a refreshingly unconventional approach".
"By using academics and Middle East experts as advisers, he sought to educate his men about the intricacies of Tal Afar. Successfully, it would seem, for his forces won over at least some of the disillusioned Turkmen population at the same time as isolating the relatively small cadre of die-hard extremists," he wrote in September 2005.
Yet despite attempts to replicate the strategy, Lt Gen McMaster himself told the New Yorker magazine the following year that constant fresh consideration was the key.
"It is so damn complex. If you ever think you have the solution to this, you're wrong, and you're dangerous. You have to keep listening and thinking and being critical and self-critical," he said.
He also spoke about some of the tragedies he witnessed during the operation in a 2007 interview with the Sunday Times, in which he spoke of the "child abuse" of al-Qaeda training young men, through often brutal means.
"I saw the most unimaginable horrors," he said. "Things you can't even imagine another human thinking of. In one case, the terrorists murdered a young boy in his hospital bed, booby-trapped the body, and when the family came to pick up the body they detonated the explosives to kill the father."
Sir Max Hastings, writing in the Guardian in 2007, called Lt Gen McMaster "the most successful unit commander to have served in Iraq" and Pulitzer Prize winner Thomas Ricks noted that his "influence already outstrips [his] rank".
He was pulled back to Baghdad in 2007 to be part of the informally-titled "Baghdad brains trust" - along with several other military academics - tasked with coming up with a fresh approach.
In the year since, he has applied his famous deep-thinking approach to his work at the Army Capabilities Integration Centre, which he began in 2008. He also served as the commander of the Army's Manoeuvre Centre of Excellence.
During this period, he was promoted up the chain of command for his contributions to his current rank, a three-star lieutenant general - the second-highest rank ordinarily achievable.