This book examines the newly emergent field of military design thinking, how it has been developed inside and outside of military doctrine, and the paradigms that underlie its key thinkers and methodologies. From the emergence of its initial methodologies in the late 1990s, military design thinking’s development rapidly accelerated in the mid-2000s in response to perceived failures of existing military doctrine and practice to adapt to the wars of the early 21st century. To establish a foundation for exploring the significance of the challenge military design thinking presented to dominant approaches to warfare, the early chapters in the book examine the ontology and epistemology of military doctrine, which is defined as a written expression of a military’s institutional belief system regarding how to wage war. They also explain how attempts to incorporate military design thinking into doctrine ultimately led to its assimilation into this belief system, requiring military design thinkers to continue to explore and develop the field outside of doctrine. Since the mid-2010s, non-doctrinal military design methodologies have become increasingly prominent within several Western militaries, including the US, Canada, UK, Australia, and several European militaries. Later chapters offer an exploration of the paradigms underlying non-doctrinal as well as doctrinal design methodologies. This book highlights how the field has evolved, shows how military design thinking differs from its ‘civilian’ equivalents developed in fields such as commerce and business management, and discusses how it may evolve in the near future. This book will be of much interest to students of military studies, security studies, and international relations, as well as to military professionals.