A new publication in the Irregular Warfare Center argues that diplomacy is a central component of modern irregular warfare, serving as a key tool for advancing U.S. interests in competition that occurs below the threshold of conventional armed conflict.
In “U.S. Diplomacy Plays Critical Role in Irregular Warfare,” author Dr. John A. Pennell examines how diplomatic engagement, coalition building, sanctions coordination, information efforts, and international partnerships have become increasingly important in today’s security environment.
The paper arrives as policymakers and defense leaders continue to assess lessons from the Russia-Ukraine war and other global conflicts, where contests over legitimacy, economic resilience, political influence, and international support have often proven as consequential as military operations on the battlefield.
Pennell argues that irregular warfare should not be viewed solely through a military lens. Instead, he points to the Department of Defense’s 2025 Irregular Warfare Instruction, which defines irregular warfare as a persistent form of competition in which state and non-state actors employ indirect, asymmetric, and often non-attributable methods to achieve strategic objectives. The guidance emphasizes that military force alone is often insufficient and that success requires coordination across government agencies, allies, partners, and international organizations.
According to the paper, diplomacy serves as one of the primary mechanisms for that coordination. Pennell describes diplomacy as the management of international relations through negotiation, representation, persuasion, and coordination, while distinguishing it from the broader concept of statecraft, which integrates diplomatic, informational, military, and economic tools in support of national objectives.
The analysis also draws on concepts developed by political scientist Joseph Nye, including “soft power” and “smart power,” arguing that modern irregular competition often centers on legitimacy, perception, influence, and political will rather than direct military confrontation.
A central theme of the paper is the role played by U.S. ambassadors and embassy country teams. Drawing on field experience, Pennell contends that chiefs of mission and diplomatic personnel frequently serve as the integrating force that brings together diplomatic, economic, informational, and security efforts in support of broader U.S. objectives.
The paper concludes that irregular warfare is increasingly shaped not only on traditional battlefields but also in embassies, foreign ministries, multilateral organizations, and sanctions coordination efforts. As competition with state and non-state actors continues to evolve, Pennell argues that diplomacy remains one of the United States’ most important instruments for building partnerships, shaping outcomes, and countering hybrid threats around the world.
