The U.S. Army has always regarded preparing for war as its peacetime role, but how it fulfilled that duty has changed dramatically over time. Preparing for War traces the evolution of the Army between the War of 1812 and World War I, showing how differing personal experiences of war and peace among successive generations of professional soldiers left their mark upon the Army and its ways.

Nineteenth-century officers believed that generalship and battlefield command were more a matter of innate ability than anything institutions could teach. They saw no benefit in conceptual preparation beyond mastering technical skills like engineering and gunnery. Thus, preparations for war were largely confined to maintaining equipment and fortifications and instilling discipline in the enlisted ranks through parade ground drill. By World War I, however, Progressive Era concepts of professionalism had infiltrated the Army. Younger officers took for granted that war’s complexity required them to be trained to think and act alike—a notion that would have offended earlier generations. Preparing for War concludes by demonstrating how these new notions set the conditions for many of the successes—and some of the failures—of General Pershing’s American Expeditionary Forces.

Reviews and recognitions:

Preparing for War has been incorporated into the West Point “Army and American Society” course curriculum and was selected for the U.S. Army Capabilities and Integration Command's professional reading list.

Preparing for War is a subtle, sophisticated, and immensely insightful contribution to U.S. military history. Combining intimate understanding with admirable critical distance, J. P. Clark’s study stands alone in describing the intellectual evolution of the army officer corps. His story may end with World War I, but its implications echo down to the present day.” — Andrew J. Bacevich, author of America’s War for the Greater Middle East: A Military History

“A unique and masterful combination of institutional, social, and intellectual history, and group biography, Preparing for War deserves a wide readership. How the army of the nineteenth century prepared for armed conflict sheds light and deep understanding on military readiness today and in the future.” — Lieutenant General (U.S. Army) H. R. McMaster, author of Dereliction of Duty: Lyndon Johnson, Robert McNamara, The Joint Chiefs of Staff, and the Lies That Led to Vietnam

“Simply put, Preparing for War is the best study of the U.S. Army before World War I in print. Clark has presented a well-written and superbly researched account of an institution undergoing transformative, cross-generational change....Guaranteed to become required reading for graduate students, Preparing for War deserves a wider audience in this politically uncertain time.” — Bobby A. Wintermute, Journal of Military History, October 2017

“Clark provides an excellent introduction to the political context within which America’s army grew from a frontier constabulary force to one of the most powerful instruments in the world. His book will prove enlightening not only for students of the past but for those interested in how our army functions within the American political system today.” — Michael S. Neiberg, author of Potsdam: The End of World War II and the Remaking of Europe

“J.P. Clark should be congratulated for his authoritative survey of the U.S. Army’s development over a turbulent century…This is an absorbing and adventurous analysis….Clark has produced a valuable synthesis of a transformative century that is rarely conceived in the round. He also has a message the resonates beyond 1917.” — Brian Holden-Reid, RUSI Journal, October/November 2018

“[Clark's] research has culminated in a magnificent new book. In this work, Clark shows us how history ought to be written — not only illuminating the past but providing a useful way to think about the future.” — Mackubin Thomas Owens, National Review, 8 May 2017

“Drawing on impressive research in primary sources and skillfully engaging scholarship...Clark tells this important story in impressive fashion....This is a study that will not be of value just to students of American military history, but to anyone interested in the challenge of adapting military institutions to change and the place of professional military education in that effort.” — Ethan S. Rafuse, History: Review of New Books, November 2017

“In this illuminating book, J. P. Clark argues that by the First World War, the army leadership had settled in favor of preparation for future war with a core of military professionals centered in the General Staff managing the mobilization of a conscript force. The fascinating story of how the U.S. reached this point and how institutional change happens is the focus of this impressive and important study.” — Graham Cross, author of The Diplomatic Education of Franklin D. Roosevelt, American Historical Review, 30 May 2018

Preparing for War is an excellent work of history. Not only is this book a fresh look at the history of the U.S. Army and the process of professional military educational reform over the course of a century, but also it provides a set of analytical tools...that may be applied in general to study change over time....These tools might be used to predict, or at least raise questions about, certain aspects of the near future.” — Lukas Milevski, author of The Evolution of Modern Grad Strategic Thought, Orbis, 9 August 2017

“J.P. Clark's Preparing for War: The Emergence of the Modern U.S. Army, 1815-1917 fills an important gap in our scholarly understanding of an important institution—the nineteenth-century US Army officer corps....Perhaps the most trenchant lesson Clark draws from his work for the current American profession of arms is a generational gap in the present US Army between general officers who led troops in Iraq and Afghanistan as senior officers, and junior officers who began their careers in those conflicts at the small unit level.” — Wayne Wei-Siang Hsieh, author of West Pointers and the Civil War, Early American Literature, June 2018

Preparing for War: The Emergence of the Modern U.S. Army, 1815–1917 is not only a well-researched and phenomenally written book, but also extremely relevant to the military as a profession. In Preparing for War JP describes the evolution of the Army following the War of 1812 up to the First World War by assessing personal experiences and the impacts of key leaders – from junior to senior levels – across this period of modern professionalism.”— Nathan K. Finney, on From the Green Notebook "Ultimate 2018 Summer Reading List," 23 May 2018

“This book is perfect for anyone looking to study organizational change, or leaders who want to impact the Army’s future. It’s also an important resource for those who wish to understand the requirements that will be placed on the military at the outbreak of another major war. Clark’s well-researched narrative is an easy read, packed full of insights and anecdotes from 100 years of Army history, and should be on every professional’s bookshelf.”  —  Joe Byerly, Army, 22 February 2018

“Like all good histories, Preparing for War proffers both a window into the past and a warning for the future. While we can learn from the experiences of previous generations, there are natural limits to how much a service can shape its own future by dint of sheer effort and enthusiasm. Clark’s compelling contribution serves as a welcome reminder––an echo of the grizzled veterans of our youth––that wars matter, and readying to fight them remains a matter of vital national interest.” —   Mike Morris, Strategy Bridge, 13 March 2018  

“Clark provides a dramatic, sweeping, and well-written study of the regular officer’s quest for professional legitimacy in the nineteenth and early twentieth centuries. In doing so, he presents a well-researched compelling account of the US Army undergoing cross-generational transformative change with connections to the larger social and cultural contexts that defined the United States and its military forces.” —   Dave BurfordH-Net Reviews, 16 December 2017  

“J.P. Clark’s masterful…Preparing for War, combines collective biography, military anthropology, and military history to illuminate the uneven tapestry of how military professions change…Clark’s work, like the best works of history, subtly illuminates current conditions….While it is unclear what shape tomorrow’s Army will take, Preparing for War represents a critical tool to understanding the future of the Army profession.” — Sam Wilkins, Small Wars Journal, 19 July 2017

“Overall, Preparing for War, is a brilliant account of the often rocky road that the Army has travelled as an organization, and, like all well-written history, is a harbinger of challenges yet to come.” — Aaron Bazin,, 12 April 2017

“The alternating and overlapping tumult of innovation and inertia, centralization and dispersion is the fascinating story of Clark’s volume, one that documents the century-long shift from the concept of the innate warrior to that of the trained careerist.” — Anthony Paletta, HistoryNet, 30 June 2017

“J.P. Clark combines his military experience and meticulous research in Preparing for War: The Emergence of the Modern U.S Army….Clark’s book intricately demonstrates that the U.S. Army was not a static institution; rather it was a living product of each generation, developing and adapting throughout the century.” —Krysten Blackstone, U.S. Studies Online, 20 July 2018