Conclusion

This report does not argue for or against the nuclear-armed sea-launched cruise missile (SLCM-N). Instead, it demonstrates a more consequential point: The value and risk of SLCM-N depend on the future strategic environment into which it is introduced. The persistent debate over the system is therefore not driven by information gaps among experts. Rather, it reflects different expectations about how future crises will unfold—how adversaries interpret U.S. actions, how technological change affects escalation control, and how much uncertainty future leaders believe can be managed. This pattern suggests that similar disagreements are likely to arise whenever new nuclear capabilities are proposed or nuclear doctrine is adjusted.

The futures tools employed in this project demonstrate that SLCM-N is most consequential only under specific conditions: when U.S. resolve is contested and escalation dynamics remain relatively predictable. Outside those conditions, its effects are limited: In some futures it adds little marginal value, while in others it risks increasing instability. No scenario supports the view that SLCM-N is either a decisive solution or an inherently destabilizing capability across all environments.

Forecasting results further indicate that the most likely trajectory toward the mid-2030s is neither stable continuity nor overt breakdown but Adaptive Deterrence: a world shaped by disruptive technological change alongside continued restraint on the part of the United States. In this environment, posture choices are judged less by their technical characteristics than by how they are perceived—particularly by China. Across scenarios, Beijing’s interpretation of U.S. intent emerges as the central factor separating stabilizing from destabilizing outcomes.

Taken together, these conclusions point to a broader methodological lesson. Forecasting and scenario-based judgment are not only possible in nuclear policy, they are necessary. Long-horizon capabilities like SLCM-N will be judged by future leaders and adversaries and in crises that differ markedly from those of today. Structured futures methods provide a way to discipline judgment despite deep uncertainty, clarify where assessments are robust or fragile, and identify the conditions under which policy choices should be revisited.

Looking forward, future nuclear policy should blend expert insight with structured futures tools rather than privileging one over the other. Expertise remains indispensable, but without methods that surface assumptions, test counterfactuals, and track changing expectations, even seasoned judgment risks becoming anchored to outdated frames. The approach used here offers a template for integrating qualitative expertise with scenario planning and probabilistic forecasting to inform decisions amid uncertainty.