Our longtime friend and colleague Ashton B. Carter departed this life abruptly and unexpectedly in October of 2022. Ash was an extraordinary figure, combining an accomplished academic career with an impressive career in government. At the Pentagon, he occupied one high-level position after another, culminating in his appointment to be Secretary of Defense. He brought to these roles a high intelligence, a passion for public service, and a relentless determination to get things done and to make a difference. And all who knew him know of his quiet but steadfast devotion to the military personnel whom he felt privileged to lead and his boundless concern and appreciation for those who sacrificed in service to their country.

When not in government, Ash was a dedicated teacher and leader at Harvard Kennedy School. He was for many years director of the Belfer Center for Science and International Affairs, where his energy, enthusiasm, and commitment to serious, policy-relevant research helped make the Belfer Center, in its field, among the most highly ranked university-based research centers in the world. Ash loved being around students, who flocked to his classes, attracted by his warmth, wisdom, sense of humor, and his genuine belief in their ability to contribute to the public good. Ash also had a long connection with this journal, serving as co-editor at an early phase of his career and later as chairman of the Editorial Board.

For those of us who worked with him and befriended him, Ash was more than just the sum of his accomplishments. He was a large and inspiring presence, a personality that filled a room and lifted up everything that he was involved in. For his family and friends, his passing is a huge and irreplaceable loss. But his absence will be felt on a wider stage as well. In these days of bitterly polarized politics and policy discourse unhinged from reason, Ash was a rare and distinctive figure: thoughtful, knowledgeable, experienced, pragmatic, reasonable, filled with integrity and concerned not with political subterfuge but with advancing the best interests of the country. He was the epitome of what a public servant should be.

A needed voice has been stilled. A treasured friend has been lost. His sudden death has left behind a stunned community that mourns the absence of its leader.

—The Editors