Read full report Within the next 10 years, U.S. extended deterrence could look notably different than it does today. In a new era of strategic competition, the twenty-first-century threat environment is changing in ways that the United States cannot readily manage or control. Nuclear threats are rising, and U.S. allies are increasingly concerned about the credibility of U.S. security guarantees. Russia is issuing veiled threats to use nuclear weapons in Ukraine, China is drastically increasing the size and diversity of its nuclear arsenal, North Korea is fielding more advanced nuclear weapons capabilities, and Iran is developing a high degree of nuclear latency. To explore these issues, the CSIS Project on Nuclear Issues leveraged an “alternative futures” methodology to unpack how key drivers might affect the U.S. extended deterrence mission in the next 10 years. In nearly all future scenarios this project explored, the United States suffers a credibility problem. It will be increasingly difficult to assure allies that the United States is prepared to employ U.S. nuclear weapons in defending their vital interests if necessary. It will require a shift in the way future administrations consult, plan, train, and operate with allies. This report is made possible by generous support from the Defense Threat Reduction Agency. The views expressed herein are those of the author(s) and do not necessarily reflect the official policy or position of the Defense Threat Reduction Agency, the U.S.