If you want to be a great leader, pay attention. The best examples often arise when you least expect them--for example, in politics.

For the first time in almost 70 years, a retired general will be the U.S. secretary of defense. That's a big deal, if you believe in civilian control of the military. But, in Marine General James Mattis, President-elect Trump has made a heck of a choice.

Even people who disagree with some of Mattis's policy positions agree that he's shown great leadership during some of the toughest circumstances. He was one of the top generals in Afghanistan and Iraq, before his military career was reportedly cut short after disputes with the Obama administration over Iran.

Here are 10 things Mattis clearly understands about what true leaders always do.

1. They commit.

Work-life balance? Please. Mattis is a lifelong bachelor with no children who spent 42 years on active duty in the Marine Corps. He's known as the warrior-monk, and his pastimes include perusing the 7,000 books in his personal library.

2. They make decisions.

There are countless examples, but let's go back 13 years to the start of the Iraq war, when Mattis relieved a colonel during the middle of combat for not achieving an objective fast enough. This is something that almost never happens in the modern military--and for not achieving an objective fast enough.

(This was dramatized in the HBO miniseries Generation Kill. It's NSFW because of language, but you might check it out.)

3. They engender passion.

If I had a dollar for every veteran in my Facebook feed cheering this move--well, I'd have a lot of dollars. Reportedly, a group of conservative billionaires tried to convince Mattis to run for president himself last year--specifically to stop Trump.

Lest you think only Republicans like him, however, Michele Clournoy, who was the frontrunner to be secretary of defense if Hillary Clinton had won the presidency, called Mattis "an outstanding candidate," and Congressman Seth Moulton of Massachusetts, a Marine veteran of Iraq, said Mattis is among a group of "leaders who can speak the truth, who aren't just constrained by the politics of the moment."

4. They communicate.

At the start of the Iraq war, Mattis published a one-page letter for the Marines under his command. Its language "become a catchphrase reprinted on bumper stickers, posters and T-shirts all over the country," as Military Times put it:

"Demonstrate to the world," Mattis said, "there is 'No Better Friend, No Worse Enemy' than a U.S. Marine."

You can find the entire letter here.

5. They demonstrate trust.

Shortly after 9/11, Mattis ordered his Marines to keep their weapons at "condition one"--meaning fully armed with a round in the chamber at all times, reminding them they were on alert 24/7.

Why is that a big deal? Because you don't do that unless you are ready to trust your troops entirely. It's simply far too easy for someone to accidentally discharge a weapon--and possibly end a general's career. Mattis did it anyway.

6. They take risks for a reason.

As a general in Iraq, Mattis "traveled the battlefield" to stay in touch with his troops, which meant that he and the small group of Marines he traveled with got "into rolling firefights outside the wire," according to The Atlantic. To put it lightly, generals don't usually get into firefights--not out of cowardice (we trust), but because the loss of a commanding general...

7. They don't filter.

Mattis's words also get him into trouble sometimes--like when he landed in Afghanistan in 2001 and announced that the Marines now "owned" a piece of the country, or later when he said this (including full context):

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. Actually, it's a lot of fun to fight. You know, it's a hell of a hoot. It's fun to shoot some people. I'll be right upfront with you, I like brawling.

Comments like that led a lot of people to predict Mattis would never reach the highest level of leadership. Now he's going to be secretary of defense.

8. They employ artistry.

Mattis's artistry is in his words. Maybe it's from reading all those books. Just search the internet for "General Mattis meme" and you'll see page after page of his quotes over his photos. My favorite? One of the rules he gave his Marines to live by in Iraq:

"Be polite. Be professional. Be prepared to kill everyone you meet."

Not a lot of room for ambiguity there.

9. They enjoy their work.

At the end of the day it seems Mattis really, really liked being a Marine and a general.

"The first time you blow someone away is not an insignificant event," Mattis once said. "That said, there are some [people] in the world that just need to be shot. There are hunters and there are victims. By your discipline, you will decide if you are a hunter or a victim."