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The Chief Scientist Research Reports (CSRRs) provide NATO’s senior political and military leadership with clear, evidence-based insight into science & technology (S&T) developments. These reports translate complex research results into actionable analysis to help the Alliance anticipate potential technological disruption, identify likely capability gaps, and adapt strategically in order to shape the future security environment and battlespace.

Foreword: Mastering the fight for the 21st century This paper is the first in a six-part series developed by CACI to reframe how national security professionals understand and engage in 21st century strategic competition. Its core argument is that Irregular Warfare (IW) — anchored in the effective use of information, influence, and other instruments of power short of armed conflict — has become a coequal dimension of strategic competition. Our adversaries wield it persistently to create advantages and impose costs without escalating to open war or prompting a U.S. military response. As the United States continues to invest in conventional deterrence, our rivals are too often winning strategic objectives through proxy warfare, disinformation, cyber aggression, legal or illicit manipulation, economic coercion, and narrative dominance. This series is intended to illuminate how the U.S. must adapt and expand — doctrinally, structurally, and cognitively — to succeed in this environment. The six papers in this series will address the following themes: 1. Defining the Environment – Understanding IW as a critical component of modern strategic competition, and aligning our doctrine, posture, and planning to compete effectively within it. 2. Gray Zone Conflicts: Redefining Victory Without Combat – Exploring how adversaries use ambiguity, information, and lawfare to shift the status quo without crossing conventional redlines. 3. Operationalizing CAPIA: Planning IW in the 21st Century – Introducing a new campaign-planning construct built around Capabilities, Access, Partnerships, Information, and Authorities — the core levers of IW success. 4. Doctrine and Authorities: Overcoming the Legal and Structural Barriers to IW – Examining the Title 10/Title 50 divide, planning gaps, and doctrinal inertia that limit IW effectiveness — and offering actionable solutions. 5. Force Design for Persistent Competition – Proposing a restructured force posture for IW dominance, from Special Operations Forces (SOF) deployment models to interagency integration and digital influence capabilities. 6. Institutionalizing IW: A Roadmap for Enduring Advantage – Providing a blueprint for integrating IW with the full range of U.S. competitive advantages — military, diplomatic, informational, and economic — while avoiding the pitfall of confining IW to a narrow “silo of excellence.” This first paper — Irregular Warfare: The Prevailing Warfighting Environment in an Era of Strategic Competition — lays the foundation. It explains why IW is the current fight, how adversaries are winning without triggering war, and what the United States must do to adapt before it is too late. The next five papers will expand the lens — from operational frameworks to structural reform — so that we are not just aware of the threat, but ready to win in its domain. BLUF: This paper examines the strategic risks inherent in deprioritizing irregular and information-centric warfare. Despite the U.S. military’s continued emphasis on conventional strength, recent policy shifts reveal a growing mismatch between our investment priorities and the evolving character of modern conflict. Adversaries are advancing their strategic aims through persistent, ambiguous, and asymmetric methods — while the U.S. remains largely focused on traditional force projection. The takeaway is clear: IW can no longer be treated as a supporting effort — it is integral to how we fight and compete.

This commentary argues that crisis response (CR)—an irregular warfare specialization executed by elite forces—can function as a strategic instrument of deterrence. Drawing on the logic of coercion and deterrence (Clausewitz; Schelling), it examines how rapid, precise operations shape adversary perceptions by exposing vulnerabilities and signaling credible, repeatable capability without provoking escalation. Hostage rescue in denied areas illustrates CR’s fungibility: the same intelligence, access, and precision required for recovery can generate wider strategic effects. Applied to the PRC–Taiwan scenario, CR complements forward posture and allied integration by imposing uncertainty on Beijing’s timelines, resources, and domestic stability. The result is a scalable framework in which crisis response extends deterrence through agility, adaptability, and cognitive advantage short of war.

When Iranian forces retook Khorramshahr in May 1982, the Iran–Iraq War could have ended. Iraq signaled readiness for a ceasefire, Iran had reversed the invasion, and the strategic balance no longer justified escalation. Yet, Tehran chose to continue the war for six more years. This decision was not simply ideological stubbornness; it marked a decisive shift in how the Islamic Republic defined victory itself. Survival, endurance, and ideological consolidation became substitutes for decisive military success. That redefinition of victory, born during the Iran–Iraq War, remains central to Iran’s strategic behavior today. From Hezbollah in Lebanon to Iranian-aligned militias in Iraq and Yemen, Tehran’s approach reflects a doctrine shaped not by triumph but by attrition, adaptation, and learning how to endure without winning outright.