Retired Marine Gen. James Mattis is sharing his insight on leadership and knife-hands.

In an online video posted by the Marine Corps, the former leader of U.S. Central Command spends more than 16 minutes answering questions from Marines and the general public that were submitted via social media.

The most revered Marine leader since the late Chesty Puller, Mattis offers leadership lessons from his time in the Corps, talking about being ordered to halt the Marines' initial advance into Fallujah in 2004 and what he was thinking when he talked to Marines one cold night in Afghanistan while walking the perimeter.

"In the Marine Corps, you're not paid to have a midlife crisis or ask people to help you through your midlife crisis," he says in one answer. "You're there to give the enemy a mid-life crisis, and that means you put your Marines together into a good, tough team."

Get ready to laugh and be inspired.