TWTR Twitter Inc

Retired Marine Gen. James Mattis, named as President-elect Donald Trump's defense secretary, doesn't agree with his presumptive new boss on every issue of national security policy. But he encompasses traits the incoming commander-in-chief evidently prizes: professional success, the esteem of peers and an edgy public image.

Where Mr. Trump campaigned on a pledge to "tear up" the Iran nuclear deal, while Gen. Mattis, though critical, said there is "no going back" on the agreement. Mr. Trump has threatened to quit longstanding security pacts because allies don't spend enough on defense; Gen. Mattis thinks that for any U.S. president to regard allies as freeloaders "is nuts."

And while Mr. Trump vowed to bring back the practice of waterboarding for overseas detainees, Gen. Mattis appeared to convince him during the course of a private meeting last month that the method wasn't useful.

Differences aside, the 66-year-old general, who retired in 2013, would bring to the administration a longtime military commander with deep battlefield experience in recent American wars, a towering reputation in the ranks and a record of friction with the Obama administration.

Mr. Trump appears particularly fond of Gen. Mattis's nickname--"Mad Dog"--using it in a Twitter message after the two met as well as at an Ohio rally on Thursday where he announced he was offering Gen. Mattis the job.

But before becoming defense secretary, Gen. Mattis faces a potentially rigorous confirmation process. Congress must adopt legislation allowing him to serve because he hasn't been out of the military for seven years, as the law requires. He also may draw scrutiny because of a four-year-long connection with Theranos Inc., the embattled blood-testing startup.

In addition to Gen. Mattis, Mr. Trump chose another retired commander, Army Lt. Gen. Mike Flynn, as his national security adviser and is considering other retired generals for top administration posts. The introduction of former military officers into jobs traditionally reserved for civilians marks a dramatic shift from the Obama administration, which became known for tension between the top military brass and civilian political appointees at the White House.

As Mr. Trump's defense secretary, Gen. Mattis would bring his own views to the administration. Mr. Trump expressed isolationist views on the campaign trail; Gen. Mattis at times has advocated more engagement abroad.

In an article for the Hoover Institution last year, he called for Congress to authorize military action against Islamic State and allow for the use of U.S. troops. He denounced limits or deadlines, writing "the time for half-measures is gone."

Gen. Mattis has advocated fighting Islamic State with battles of annihilation rather than attrition. "So the first time they meet the forces that we put against them, there should be basically no survivors," he said in a March 2015 interview.

His views come from years of commanding U.S. forces in Afghanistan and Iraq and deep involvement in key fights in both wars, including the battle of Fallujah in Iraq in 2004. He has a penchant for blunt talk and a colorful reputation that has earned him a series of nicknames, including "Mad Dog" and "Chaos."

He drew criticism from American Muslims for a frequently noted 2005 panel discussion in San Diego, telling the audience that "it's fun to shoot some people."

"You go into Afghanistan, you got guys who slap women around for five years because they didn't wear a veil," Gen. Mattis said at the time. "You know, guys like that ain't got no manhood left anyway. So it's a hell of a lot of fun to shoot them."

A 2006 book on the Iraq war by former Washington Post and Wall Street Journal reporter Thomas Ricks disclosed a rule given by Gen. Mattis to troops in Iraq: "Be polite, be professional, but have a plan to kill everybody you meet."

While known for such hard-edged quotes, the unmarried former Marine Corps officer is also considered deeply scholarly, earning another nickname, the "warrior monk." He brought a copy of the Roman emperor Marcus Aurelius' writings with him while deployed abroad to remind himself of the timelessness of impulses, challenges and solutions in warfare.

An accomplished strategist, Gen. Mattis helped develop the military's counterinsurgency doctrine and an approach aimed at winning the support of local populations.

Over his career, he rose through the ranks from enlistee to four-star general, ultimately becoming chief of U.S. Central Command under President Obama in 2010, a position he held until his retirement three years later.

The administration announced his successor earlier than was necessary, a move that had the effect of undercutting Gen. Mattis and spurred a belief on Capitol Hill that he had been treated unfairly by the White House. The Obama administration also drew criticism for forcing Gen. Flynn out of his post as head of the Defense Intelligence Agency.

Since leaving the military, Gen. Mattis has been a visiting fellow at the Hoover Institution and has served on corporate boards, including Theranos and General Dynamics Corp., the defense contractor and aerospace firm.

Military subordinates have praised both his strategic aptitude and his loyalty to troops. In 2001, he declined a sleeping cot until all his Marines had their own.

Experts said Gen. Mattis could fill an important role as the Trump administration sets about defining what it sees as the U.S. role in the world.

"Mattis never enters a knife fight without a strategy. He has a plan A, plan B and plan C," said Glen Howard, who has worked as a consultant to U.S. national security agencies and is president of the Jamestown Foundation, a think tank in Washington.

"He knows the geopolitical chessboard and knows the utility of American power and how to use it and when not to use it," Mr. Howard said. "I think the message Trump sends by picking Mattis is that when he talks to [Russian President Vladimir] Putin, Mattis will be nearby."

Write to Paul Sonne at paul.sonne@wsj.com, Gordon Lubold at Gordon.Lubold@wsj.com and Julian E. Barnes at julian.barnes@wsj.com

(END) Dow Jones Newswires

December 07, 2016 08:25 ET (13:25 GMT)

Copyright (c) 2016 Dow Jones & Company, Inc.