Donald Trump considering retired Gen. James Mattis for secretary of defense

"Chaos" may return to America's overseas policies, with reports Jim Mattis, the retired Marine general who used that term as his radio call sign, is among President-elect Donald Trump's top considerations for secretary of defense.

The former commander of U.S. conflicts in the Middle East met with Trump on Saturday, with the president-elect tweeting later that Mattis "was very impressive yesterday. A true General's General!"

Throughout his 44-year career in the Marine Corps, Mattis gained a reputation as an aggressive combat commander, a straight talker and a leader who gained almost legendary status among his fellow Marines, who continue to recount unconfirmed stories like when Mattis, unmarried, relieved a duty officer on Christmas Eve so the young man could spend it with his family.

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Mattis remains a popular figure in Congress, particularly among members of the Senate Armed Services Committee. His status likely would help his prospects of being confirmed and granted the waiver he would need to circumvent regulations requiring the defense secretary to have been out of military service for at least seven years before holding the post.

The 66-year-old Washington state native's comments both in and out of uniform indicate he would advise a much more aggressive U.S. posture abroad, though not necessarily one that would involve military action.

Shortly after retiring in 2013, Mattis revealed his top concern while overseeing conflicts in the Middle East as head of U.S. Central Command: "Iran, Iran and Iran," he told the Aspen Security Forum, referring to the topic he would discuss first with his briefers each day.

The Obama administration was at that time in the midst of negotiating with Iran on the since finalized deal to curb its nuclear capabilities. Trump has said he would tear up the pact.

But Mattis also warned in his 2013 remarks that despite its nefarious activities across the Middle East and nearby regions, Iran's nuclear ambitions could not be tamed with military power alone.

"Certainly it can be delayed a month, 6 months, 18 months. What do you do with the delay is the question," he said. "The military can buy our diplomats some time, but it cannot solve this problem straight up."

Mattis' exploits on the battlefield and leadership style earned him other nicknames, like "Mad Dog" and the "Warrior Monk." He also gained fame through a series of maxims, such as a segment from a letter he sent throughout the 1st Marine Division ahead of leading it in the initial invasion of Iraq in 2003: "Engage your brain before you engage your weapons."

In advice he offered his troops about what to do once conventional combat gave way to fighting an insurgency, he stated: "Be polite, be professional, and have a plan to kill everyone you meet."

Mattis' aggressive style has wrought controversy at times. At a forum in San Diego in 2005, Mattis said "it's a hell of a hoot" and "fun to shoot some people. I'll be right up there with you. I like brawling."

"You go into Afghanistan, you got guys who slap women around for five years because they didn't wear a veil," he said. "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."

That kind of rhetoric is perhaps part of what appealed to Trump, who in an October presidential debate said he would "knock the hell out of" the Islamic State group.

More recently, Mattis has offered deep public criticism of what he sees as a reactionary U.S. war policy abroad, particularly in Iraq and Syria amid the Syrian civil war and as the U.S. fights the Islamic State group. President Barack Obama has worked not to commit American "boots on the ground" in the region, though that pledge has subsequently morphed into a refusal to commit large formations of combat troops to war zones.

Mattis has argued that America's national security posture has simply appeared indecisive.

"[We need to] come out from our reactive crouch and take a firm, strategic stance in defense of our values," he told Congress last year, testifying alongside former Army Vice Chief of Staff Gen. John Keane, a Trump campaign adviser.