The war in Ukraine has demonstrated the enduring relevance of nuclear weapons in international politics. The Fragile Balance of Terror, edited by two established thought leaders in this field, demonstrates this through a tour de force of US scholars at the cutting edge of contemporary nuclear scholarship. The book demonstrates how enduring challenges such as the limitations of nuclear learning, the impact of command and control, and the psychology of personalist leaders remain pressing and ever more complex. Cold War scholarly and policy issues are resurfacing and increasing in the new era of great power competition, more and increasingly diverse nuclear states, and new technologies. The book also demonstrates the limitations of established approaches. For example, Cold War literature on nuclear dyads is insufficient to deal with multipolar nuclear competition, and when gauging the impact of new information and surveillance technologies on crisis dynamics. The Fragile Balance of Terror sounds an alarm bell in terms of the gravity of the policy challenge nuclear weapons will pose in the decades to come. As the editors conclude, the book's insights reduce our confidence that deterrence and luck will continue to spare the world of nuclear use as it has since 1945. The silver lining is that this book demonstrates the strength and capacity of a growing strategic studies community to cope with those same challenges.