Ash Carter is a physicist and a defense-policy expert, having served in government periodically for decades. He was secretary of defense from 2015 to 2017. He has spent his academic career at Harvard, where he is today. In this “Q&A,” Jay Nordlinger asks him about some of the biggest issues: nuclear proliferation, North Korea, Iran, the size of the U.S. military. He also asks about the relation between our servicemen and the general American population. Is there too great a gulf between them? Do people sentimentalize our military? Is it okay to say “Thank you for your service”?

On December 11, 2016, just before my time as secretary of defense ended, I stepped off a C-130 transport plane onto a cold and dusty patch of northern Iraq that had been on my mind for more than a year: an Iraqi military airfield called Qayyarah West. Q-West was a talisman of progress on one of the defining issues of my service, the fight to defeat ISIS. A year before, General Joe Dunford and I had briefed President Obama on a plan to step up the fight against ISIS.

How America, together with her friends and allies, turned the tide against a common enemy is a story of good fortune, critical leadership decisions, and skill and bravery on the part of young men and women in uniform.

"The liberation of Mosul and the inevitable, approaching liberation of Raqqa in Syria will not be the end of the Islamic State and its evil ideology. But they crush the group’s pretense to having an actual “state” based upon it. As its surviving leaders scurry to the corners of the desert, no longer can they claim to head a winning movement. Their defeat diminishes the inspiration for violent extremists, or simply lost souls on social media, to attack Americans and our friends. This is a necessary step forward in combating terrorism. Americans are safer for it."

Dr. Ashton B. Carter and Ambassador Robert G. Joseph discuss recommendations stemming from recommendations in final report of the review they co-chaired of the Defense Threat Reduction Agency (DTRA) and other DOD efforts to counter weapons of mass destruction.

PDP Co-Director Ashton B. Carter testifies before the Senate Committee on Homeland Security and Governmental Affairs.

This report of the International Security Advisory Board (ISAB) offers nineteen recommendations for discouraging a cascade of nuclear weapons states.

This National Security Advisory Group report provides a new comprehensive strategy for reducing nuclear threats and preventing nuclear terrorism.

Failure to develop a comprehensive contingency plan, such as the one proposed here, and inform the American public, where appropriate, about its particulars will only serve to amplify the devastating impact of any nuclear attack on a U.S. city