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 3, 2015, then Secretary of Defense Ash Carter made an announcement that would transform the U.S. military: all combat jobs in every branch of the military would be open to women. At a Harvard Kennedy School event this fall, Carter talked about his historic decision.

By working together, I am confident we can succeed, because in many ways we already have. If we think back to those defense investments and decisions that changed the course of our nation’s and our military’s history for the better — and not just in technologies like GPS, the Internet, and satellite communications, but also in other areas, like the all-volunteer force — they were all able to benefit our security and our society because they garnered support across the aisle, across branches of government, and across multiple administrations.

Nineteen years ago, I was in Ukraine when the last nuclear warheads, orphaned during the Soviet Union’s breakup, rolled out of the country. As an assistant secretary of Defense at the time, I had worked with Washington colleagues and foreign counterparts to eliminate those nuclear weapons and thus one danger at the dawn of the post-Cold War world. Together — with bipartisan support in Congress led by Sens. Sam Nunn, a Democrat, and Richard Lugar, a Republican — we succeeded.

Today, the Iran deal provides the opportunity to address an even greater nuclear threat. Congress should support it because, once implemented, the deal will remove a critical source of risk and uncertainty in a vitally important but tumultuous region.

"Iran's continued pursuit of an illicit nuclear program and North Korea's rash intimidation after sinking a South Korean navy ship are but the most recent reminders of the real need for effective U.S. missile defenses," write Under Secretary of Defense for Policy Michele Flournoy and Under Secretary of Defense for Acquisition, Technology and Logistics Ashton Carter.

President Barack Obama announced Monday that he has nominated Dr. Ashton B. Carter to serve as Under Secretary of Defense for Acquisition, Technology and Logistics.

PDP Co-Director Dr. Ashton B. Carter explores the daunting list of national security challenges facing the next American president.

A Task Force sponsored by the National Security Initiative, a program of the Bipartisan Policy Center, released a ground-breaking report identifying the regional and global threats posed by a nuclear weapons-capable Iran and recommending a new, robust and comprehensive strategy designed to prevent Iran from acquiring nuclear weapons capability.

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.

A key challenge for the next administration's national security leadership concerns the management of investment in the U.S. national security future. In this paper for the Aspen Strategy Group, Dr. Ashton Carter discusses the challenges of defense budgeting and program selection, and the current mismatch between resources and strategy.