Sec. of Defense James Mattis, known for his frank quotes about the realities of war, offered up a line befitting his nickname, “Mad Dog,” during an interview airing Sunday.

“What keeps you awake at night?” CBS “Face the Nation” host John Dickerson asked Mattis.

“Nothing,” a stonefaced Mattis responded. “I keep other people awake at night.”

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Mattis’ remark is sure to join a long list of the former Marine general’s most memorable quotes.

“When you men get home and face an anti-war protester, look at him in the eyes and shake his hand. Then, wink at his girlfriend because she knows she’s dating a pussy,” Mattis once said. (RELATED: These Are The 7 Most Alpha Quotes From James Mattis)

“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 told Iraqi leaders during the 2003 invasion.

“Be polite, be professional, but have a plan to kill everybody you meet,” Mattis was known to tell Marines under his command during the Iraq war.

In his interview with Dickerson, Mattis discussed the U.S. military’s shift in strategy in the fight against ISIS. “Annihilation” rather than “attrition” is the goal now, he said.

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WATCH DAILY CALLER’S VERSION OF MATTIS’ QUOTE:

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