Judy Woodruff:

Now to my interview with former Secretary of Defense retired Marine Corps General James Mattis. He resigned in protest just before Christmas last year after President Trump announced that he would pull American forces out of Syria.

The U.S. and its allies were trying to finish off the remnants of the ISIS caliphate, and Mattis wrote in his resignation letter that he believed Mr. Trump deserved a secretary of defense whose — quote — "views are better aligned with yours."

The decorated Marine served more than four decades in uniform, including commands in both Iraq and Afghanistan. He left the Corps in 2013 after a tumultuous turn running U.S. Central Command under President Obama.

Secretary Mattis has written a new book, "Call Sign Chaos: Learning to Lead."

And I sat down with him this morning in New York City.

Former Secretary James Mattis, thank you very much for talking with us.