Gen. James Matttis' legion of admirers call him either “the Warrior Monk” or “Mad Dog.” | Getty 9 unforgettable quotes by James Mattis

James Mattis, the retired Marine Corps general who has been tapped to be Donald Trump’s secretary of defense, is known for his earthy aphorisms -- eminently quotable, often controversial observations on everything from the romanticism of war to the secret of personal success (“I don’t lose any sleep at night over the potential for failure. I cannot even spell the word,” he once said.)

Reporters who have followed the arc of the four-star general’s 44-year military career from the sands of Iraq to the halls of the Pentagon have dubbed his many pithy statements “Mattisisms”; his legion of admirers call him either “the Warrior Monk” or “Mad Dog.” One Mattisism -- “be polite, be professional, but have a plan to kill everybody you meet" -- even made it into a popular video game.

It turns out that Mattis, whose gruff exterior masks a finely honed intellect, may have influenced the president-elect’s view on waterboarding with something of a Mattisism. Trump told The New York Times that he was “surprised” when Mattis told him he does not favor the practice.

“He said, ‘I’ve never found it to be useful,’” Trump relayed. “He said, ‘I’ve always found, give me a pack of cigarettes and a couple of beers and I do better with that than I do with torture.’ And I was very impressed by that answer.”

Here’s a sampling of Mattis’ most memorable quotes:

1. ‘It’s quite fun to shoot them, you know. It’s a hell of a hoot. It’s fun to shoot some people.’

In 2005, he offered this commentary on war: “You go into Afghanistan, you got guys who slap women around for five years because they didn't wear a veil. 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.”

He continued: “Actually it's quite fun to fight them, you know. It's a hell of a hoot. It's fun to shoot some people. I'll be right up there with you. I like brawling.”

At the time, after the remarks made some waves, Marine commandant Gen. Michael Hagee noted that Mattis “often speaks with a great deal of candor.”

2. ‘There are some assholes in the world that just need to be shot.’

Speaking to some 200 Marines, Mattis had this advice, according to longtime reporter Thomas Ricks: “The first time you blow someone away is not an insignificant event. That said, there are some assholes in the world that just need to be shot.”

Mattis elaborated, “There are hunters and there are victims. By your discipline, cunning, obedience and alertness, you will decide if you are a hunter or a victim. It’s really a hell of a lot of fun. You’re gonna have a blast out here!”

And: “I feel sorry for every son of a bitch that doesn’t get to serve with you.”

3. ‘I come in peace. I didn’t bring artillery. But I’m pleading with you, with tears in my eyes: If you fuck with me, I’ll kill you all.’

Mattis remembered offering this message to Iraqi leaders following the invasion, Ricks reported.

4. ‘Be polite, be professional, but have a plan to kill everybody you meet.’

According to the same report, Mattis advised his Marines in Iraq to stay vigilant. In that vein, he also once said, “There is only one ‘retirement plan’ for terrorists.”

5. ‘There are some people who think you have to hate them in order to shoot them. I don’t think you do.’

“It’s just business,” Mattis said.

6. ‘In a country with millions of people and cars going everywhere, the enemy is going to get a car bomb out there once in awhile.’

Matt was characteristically blunt in a 2007 interview with the San Diego Union-Tribune. “There are going to be good days and bad days. Bottom line,” he concluded.

7. ‘PowerPoint makes us stupid.’

Mattis gets a third of his briefings on the presentation platform, though, The New York Times has reported.

8. ‘I get a lot of credit these days for things I never did.’

For all his proverbial outspokenness, in a 2004 speech at the Naval Academy, Mattis was reportedly modest about his accomplishments.

9. “Engage your brain before you engage your weapon.”

Mattis, a student of counterinsurgency tactics and strategy, sent this advice to his Marine unit only a few hours before they helped kick off the 2003 invasion of Iraq. “While we will move swiftly and aggressively against those who resist, we will treat all others with decency, demonstrating chivalry and soldierly compassion for people who have endured a lifetime under Saddam’s oppression,” he wrote.