He’s a history buff. He’s a legendary United States Marine. And, as of recently, he’s in line to be America’s next defense secretary.

He’s retired General James “Mad Dog” Mattis, and according to at least one veteran who once served under him while deployed overseas, he’s “an incredible leader.”

Here’s Marine vet Nate Fick — once a captain and second lieutenant under Mattis in Afghanistan — backing up his lofty claim with a story, as told to Business Insider:

It was a cold night in Dec. 2001 at the Marines’ patrol base in Kandahar, Fick recalled. They had been patrolling outside of the base, but once they were back, Fick had ordered his Marines to have two men awake in each hole on perimeter security, while everyone else slept.

“I was out walking the lines one night at 2, maybe 3 a.m.,” Fick said, adding that he was coming closer to a fighting hole his Marines were manning. “As I got closer, I saw a third head.”

He was initially angry that there was another Marine either not sleeping or away from the hole they were supposed to be in, but then he realized, “It was General Mattis.”

“He had stopped to talk to the sergeant and the lance corporal.”

Mattis was doing the same thing that Fick was doing: Checking on the junior Marines.

“Nobody would’ve criticized Mattis if he had a lieutenant like me heating up his MREs and if he stayed inside to sleep on a cot,” Fick said.

“But Mattis understood that it all comes down to personal leadership. He’s the classic fighter leader. He’s the player coach. He’s out there with his troops,” he explained.

“You can have all the staff meetings you want, but there’s no substitute for walking around and talking to people who do the work.”

In the piece, other Marines detail their stories, and they’re equally as impressive. One tells of the time he relieved him of his duty to spend time with his family on Christmas, while another recalls a speech Mattis gave them “like an articulate warrior scholar as he simultaneously praised us with unrepeatable expletives.”

There’s also the following letter, which was given to members of the 1st Marine Division in 2003, right before the invasion of Iraq:

mattis-letter-photo-for-post

“On your shoulders rests the hope of all mankind. Carry out your mission and keep your honor clean. Demonstrate to the world there is ‘No Better Friend, No Worse Enemy.'”