WASHINGTON – Those who have served with and worked alongside Army Lt. Gen. H.R. McMaster, President Trump’s new national security adviser, describe a brilliant leader and military strategist they would follow anywhere.

“I’d follow him to battle in hell if he’d asked me to,” said Army Sgt. Maj. Donald Sparks, who deployed with him to Iraq in 2005.

Sparks was with then-Col. McMaster, commander of the 3rd Armored Cavalry Regiment, when a roadside bomb hit his Humvee on April 17, 2005, in Latifyah, Iraq.

Sparks recalls that after exiting the Humvee to repel the ensuing attack, “eventually I found myself back to back with my commander.”

“That’s the type of leader he was and is,” he said. “He’ll be right there in the thick of the fight and his presence will calm those in the fight.”

It was also the first time during the Third Army Cavalry’s deployment that a soldier was killed. The attack was detailed in an April 21, 2005 Washington Post story titled “Horror Glimpsed from the Inside of a Humvee in Iraq.”

“I watched him pin Purple Hearts on the wounded, speak to grieving troopers at memorial services, and shed tears for the fallen,” Sparks added. “I could go on and on. … He looks great with those stars.”

Sparks is not the only person to revere the commander, whose efforts in the northern Iraqi city of Tal Afar is credited with helping inform the counterinsurgency strategy that Gen. David Petraeus implemented throughout the country.

Sen. Tom Cotton (R-AR), who recommended McMaster for the position, also served under him in Iraq. Cotton submitted his resignation from the army in 2007, partly because he was passed over for a promotion to a one-star general. He later rescinded that resignation to deploy to Afghanistan.

“H.R. McMaster is one of the finest combat leaders of our generation and a great strategic mind. He is a true warrior scholar, and I’m confident he will serve both the president and the country well,” he said.

Ret. Army Col. Joseph Collins, director of the Center for Complex Operations at National Defense University, added, “He is also a lovely man who will call and email his friends and subordinates in their times of need. I don’t know anyone who has worked for him who doesn’t admire him greatly.”

In Tal Afar, McMaster commanded the 3,500-soldier brigade, defying the official strategy of training Iraqi forces to effect a quick withdrawal. Instead, he fanned his forces out in the town, establishing dozens of small outposts and focusing on improving security and restoring services for civilians.

The strategy, along with a troop surge, would help turn the tide of the war.

McMaster, 54, has built a reputation as one of the army’s best thinkers of his generation. He is frequently described as a “100-pound brain.”

“He’s a very thoughtful, deep thinker. He reads Thucydides — he was quoting him the other day at an event at IISS,” said Mark Fitzpatrick, executive director of the International Institute for Strategic Studies-Americas.

Friends also say he is honorable.

“He is brilliant and principled. He speaks truth to power and that has occasionally rubbed some of his peers and superiors the wrong way,” said Collins.

McMaster was twice passed over for promotion to general, before Petraeus, one of his biggest supporters, and then-Defense Secretary Robert Gates rallied support for him.

McMaster wrote the book on military commanders speaking truth to power, which some say could cause him to collide with others at the White House.

His PhD dissertation at the University of North Carolina at Chapel Hill would later become the 1997 book Dereliction of Duty, written about how the joint chiefs of staff did not stand up to President Lyndon B. Johnson during the Vietnam War, even though they disagreed with his strategy.

He also served on an informal “Council of Colonels,” created by former Chairman of the Joint Chiefs of Staff Adm. Peter Pace to critique the Iraq War strategy.

“He has a forceful personality. He doesn’t suffer fools well. If he thinks somebody’s wrong, he won’t hesitate to say so,” Fitzpatrick added.

Fitzpatrick predicts McMaster will get along with Defense Secretary Jim Mattis, who reportedly had battled over political appointments with former National Security Adviser Michael Flynn, a retired army lieutenant general.

“They’re kind of birds of a feather. … I think he’ll play well with [Secretary Rex] Tillerson at the State Department. But others in the White House — that’s the big question. How well they play with him is maybe the question.”

The West Point graduate has not served a long tour at the Pentagon or Washington, D.C., which could make it challenging to help coordinate President Trump’s national security strategy among the different agencies.

Regardless, McMaster has many fans rooting for him, even among Trump’s fiercest critics.

Senate Armed Services Committee Chairman John McCain (R-AZ) said in a statement, “I could not imagine a better, more capable national security team than the one we have right now.”

McMaster was previously director of the Army Capabilities Integration Center at Fort Eustis, Virginia. He is also known for commanding a unit during one of the biggest tank battles of the Persian Gulf war in 1991, where he earned the Silver Star.