In February, the Pentagon released a new Nuclear Posture Review (NPR), a comprehensive overview of the nation’s nuclear forces, their disposition, and plans for the future. Here, Belfer Center experts share their assessments of this NPR and the future of America’s nuclear capabilities.

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."

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.

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.

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.

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