Ash Carter participates in panel discussions at the 2018 World Economic Forum in Davos.

Former U.S. Defense Secretary Ash Carter provides insight on North Korea's threats ahead of the Winter Olympics on CNBC's Squawk Box.

The last time that America almost risked a pre-emptive strike on North Korea the gamble offered a spectacular pay-off. Ashton Carter, a leading architect of that plan, recalls that his scheme for bombing the Yongbyon nuclear facility in 1994 assumed that in one or two days the entirety of the regime’s nuclear programme could be levelled and entombed in rubble. Mr Carter, who went on to become defence secretary in the Obama administration, now thinks that an American first strike would only put “a significant dent” in North Korea’s arsenal of nuclear devices and bombmaking sites. “The difference today is that the North Koreans are very good at hiding, burying and moving around their nuclear infrastructure,” says Mr Carter, now at Harvard University.

"To pin too much hope" on China curbing North Korea's behavior "is unrealistic," former US Defense Secretary Ash Carter tells Christiane Amanpour.

Andrew Poulin, President of the Center for International Maritime Security, interviews Belfer Center Director Ash Carter.

Ash Carter, the 25th Secretary of Defense and the Director of the Belfer Center, talks with Aroop Mukharji (@aroopmukharji) about how he connected the technology industry with the Defense Department through DIUx, the tensions between the President and his cabinet, and what lessons we can learn from medieval history.

Ash Carter, the 25th Secretary of Defense and the Director of the Belfer Center, talks with Aroop Mukharji (@aroopmukharji) about how he connected the technology industry with the Defense Department through DIUx, the tensions between the President and his cabinet, and what lessons we can learn from medieval history.

To ministers and heads of state, he was a sought-after adviser, pointing the way toward reforms that boosted farm yields, educational standards, and economic prosperity. To the scientific community, he was an unstinting champion of innovation and rigorous evidence. To his students, he was a passionate teacher and mentor. To thousands of his fans on social media, he was a fount of insight, optimism, and good humor. To us, he was a dear friend and extraordinary colleague.

As former Defense Secretary, Ash Carter is no stranger to high-pressure situations. Yet he recalls these intense experiences in a measured tone, describing his reactions and rationales in precise detail. Methodical decision-making, he explains, is a critical skill of someone in his position, saying, "If you're going to make an important decision, you have to make sure that you have buttoned it down."

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”?