Everything you need to know about Trump's new national security adviser HR McMaster Gen. McMaster is taking over for Michael Flynn, who resigned.

 -- Army Lt. Gen. H.R. McMaster, a West Point graduate who was awarded the Silver Star during the Gulf War, was chosen to be Donald Trump's new national security adviser, replacing Michael Flynn, who resigned last week following the revelation that he misled Vice President Mike Pence about his conversations with Russia.

McMaster, who will remain on active duty, joins former generals James Mattis, the secretary of Defense, and John Kelly, the secretary of Homeland Security. He’s considered a creative thinker in intelligence circles, and his counterinsurgency strategies in Iraq led to the U.S. Army securing the city of Tal Afar in 2005.

He also took a critical look at the prosecution of the Vietnam War for his Ph.D. thesis, which he later published as a book.

Here is what you need to know about McMaster, who is expected to remain on active duty while working with Trump:

Name: Herbert Raymond McMaster

Age: 54

His last job: McMaster has been the director of the U.S. Army Training and Doctrine Command’s Army Capabilities Integration Center since July 2014, which is tasked as the lead architect of the Army.

What he used to do: He made a name for himself as a cavalry commander in the Gulf War, where he was awarded a Silver Star for his leadership in destroying more than 80 Iraqi tanks using nine American ones. He later led troops in the Iraq War, where in 2005 he helped recover the city of Tal Afar using innovative military strategies. He was the director of Concept Development and Learning at the Army Training and Doctrine Command from 2008-2010, and served as the commanding general at the Maneuver Center of Excellence at Fort Benning before taking the director position at the Army Capabilities Integration Center.

Hometown: Philadelphia

Family: McMaster is married to Kathleen Trotter McMaster. In Tom Clancy’s 1994 book “Armored Cav,” McMaster said he met his wife while he was playing rugby for the Army team at West Point in 1983. They have three daughters, Katharine, Colleen and Caragh.

Education: He graduated from the U.S. Military Academy at West Point in 1984, and received his Ph.D. in military history from the University of North Carolina at Chapel Hill.

What you might not know about him: He also worked as an assistant professor of history at the U.S. Military Academy in the mid-90s.

What he has said or written about national security objectives:

McMaster has been known to speak his mind on military strategy, even when it goes against the status quo. He’s faced delays in promotions at the level of major and colonel, which some suspect were a result of his iconoclastic views.

His doctoral dissertation on the Vietnam War became his first book, “Dereliction of Duty.” The book is a blistering critique of the Joint Chiefs of Staff, who he argued failed to provide necessary military advice to President Lyndon B. Johnson and Secretary of Defense Robert McNamara.

In the conclusion to the book, McMaster wrote, “The war in Vietnam was not lost in the field, nor was it lost on the front pages of the New York Times or the college campuses. It was lost in Washington, D.C."

“Dereliction of Duty” has been recommended reading for Army officers since it was published in 1997.

He’s also notably criticized the way the Bush administration entered the war in Iraq, and last year he told a Senate panel that he feared the Army might become too small to adequately secure the country.

While he has been praised for his military strategy and his willingness to speak up, both McMaster and National Security Council Chief of Staff Keith Kellogg have little experience with government outside of the Army.