‘Mad Dog’ Mattis is asked what keeps him awake at night…

Secretary of Defense James “Mad Dog” Mattis is known for his brutally honest quotes about war and his overall effectiveness as a military leader. Upon his retirement from the Marine Corps, the Marine Corps Times named him the “most revered Marine in a generation.”

On Sunday, Mattis personified his reputation during an interview with CBS “Face the Nation” host John Dickerson.

During the wide-ranging interview, Dickerson and Mattis discussed the number of threats currently facing America, like unrest in the Middle East, the Islamic State and North Korea.

But when Dickerson inquired what keeps him up at night, Mattis didn’t hesitate to answer.

“What keeps you awake at night?” Dickerson asked.

Without skipping a beat or batting an eye, Mattis replied: “Nothing. I keep other people awake at night.”

Indeed, Mattis was dead serious.

The 4-star Marine general is known for his memorable quotes. See some below:

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

I don’t lose any sleep at night over the potential for failure. I cannot even spell the word.

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

The most important six inches on the battlefield is between your ears.

The quote, which came during Memorial Day weekend, was widely praised on social media: