The Past, Present, and Future of U.S. Ground Interventions Identifying Trends, Characteristics, and Signposts Jennifer Kavanagh, Bryan Frederick, Matthew Povlock, Stacie L. Pettyjohn, Angela O’Mahony, Stephen Watts, Nathan Chandler, John Speed Meyers, Eugeniu Han C O R P O R A T I O N For more information on this publication, visit www.rand.org/t/RR1831 Library of Congress Cataloging-in-Publication Data is available for this publication. ISBN: 978-0-8330-9776-7 Published by the RAND Corporation, Santa Monica, Calif. © Copyright 2017 RAND Corporation R® is a registered trademark. Front cover photo by Capt. Tim Irvin, U.S. Army Limited Print and Electronic Distribution Rights This document and trademark(s) contained herein are protected by law. This representation of RAND intellectual property is provided for noncommercial use only. Unauthorized posting of this publication online is prohibited. 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Support RAND Make a tax-deductible charitable contribution at www.rand.org/giving/contribute www.rand.org Preface This report documents the results of the project “Past and Future Trends in U.S. Army Interventions.” The project analyzed historic trends in U.S. ground interventions, identified factors that influence the likelihood and size of these interventions, and identified potential signposts of future interventions that can be used by Army planners to better anticipate and plan for future interventions. The findings should be of value to a wide-ranging audience in the defense and foreign policy community, including those with an inter- est in gaining a greater understanding of past trends and patterns in U.S. ground interventions as well as those seeking to gain insight into the pos sible drivers, characteristics, and locations of potential future interventions. The signposts presented in this report will be particularly useful for Army planners and strategists who may be able to use the metrics and analysis provided here to improve planning and respon- siveness for future ground interventions. This research was sponsored by the Office of the Deputy Chief of Staff, G-3/5/7, United States Army Headquarters, and conducted within the RAND Arroyo Center’s Strategy, Doctrine, and Resources Program. RAND Arroyo Center, part of the RAND Corporation, is a federally funded research and development center sponsored by the United States Army. The Project Unique Identification Code (PUIC) for the project that produced this document is HQD146865. iii Contents Preface ............................................................................. iii Figures ............................................................................. ix Tables .............................................................................xiii Summary ........................................................................ xvii Acknowledgments ............................................................ xxxi Abbreviations ................................................................. xxxiii CHAPTER ONE Introduction ....................................................................... 1 Study Approach .................................................................... 3 Organization of This Report ...................................................... 5 CHAPTER TWO Historical Analysis of U.S. Army Interventions ............................ 7 RUGID .............................................................................. 8 Variables in the Intervention Data ............................................11 Variables in the Unit Type Data ..............................................14 Historical Trends in U.S. Ground Interventions ..............................16 Trends in Activity Types .......................................................17 Trends in Location ............................................................. 20 Trends in Duration and Size ................................................. 22 Analysis of Unit Types in U.S. Ground Interventions ....................... 27 Trends in Unit Type Use ...................................................... 27 Relationship Between Unit Type and Activity ............................. 30 Relationship Between Unit Type and Intervention Size ...................32 Unit Type Mismatches and Shortages ........................................35 v vi The Past, Present, and Future of U.S. Ground Interventions Summary: Which Units Are Most Stressed? ............................... 38 Has the United States Intervened in the Past? .................................39 Interventions into Armed Conflict .......................................... 40 Stability Operations ........................................................... 43 Deterrent Interventions ....................................................... 44 Implications..................................................................... 46 Summary and Implications ......................................................47 CHAPTER THREE Determinants of the Likelihood and Size of Interventions ..............49 Existing Literature and Its Shortcomings ..................................... 50 Characteristics of the International Environment ......................... 50 Characteristics of the Conflict or Crisis ......................................52 Domestic Characteristics of the United States ............................. 54 Characteristics of the Target State ............................................59 Characteristics of the Relationship Between the Target State and the United States ......................................................61 U.S. Interests ....................................................................62 Limitations of Existing Research..............................................63 Identifying Determinants of the Likelihood and Size of Ground Interventions .............................................. 64 Methodology: An Overview .................................................. 66 Interventions into Armed Conflicts ..........................................70 Interventions to Conduct Stability Operations ............................. 77 Interventions to Increase Deterrence .........................................83 Summary and Implications ..................................................... 88 CHAPTER FOUR Clustering .........................................................................93 What Is Intervention Clustering? ...............................................93 A Look at the Data ............................................................... 94 Why Would Interventions Cluster? A Review of Existing Literature .......95 Mechanisms of Intervention Clustering ....................................... 99 Approach ......................................................................... 101 Results ............................................................................ 103 Summary and Implications .................................................... 107 Contents vii CHAPTER FIVE Case Studies..................................................................... 111 Why Use Case Studies? Purpose and Methodology ........................ 111 Case Study Insights and Takeaways .......................................... 114 Lead Time, Duration, and Withdrawal .................................... 114 Resource Demands and Constraints ....................................... 120 Leading Indicators and Warning Signs of Future Interventions ........ 127 Summary and Implications .................................................... 135 Ties to Statistical Analysis ..................................................... 137 CHAPTER SIX Signposts of Future Interventions .......................................... 139 Defining a Signpost ............................................................. 139 Signposts for Interventions into Armed Conflict ............................ 140 Relationship with the United States ........................................ 140 Destructiveness of the War .................................................. 143 Previous Intervention ......................................................... 145 War Weariness ................................................................ 146 U.S. Capabilities .............................................................. 148 Attack on U.S. Soil ........................................................... 150 Public and Elite Opinion .................................................... 150 Signposts of Stability Operations Interventions ............................. 151 Location of the Target ........................................................ 151 Number of Refugees .......................................................... 152 Involvement in the Combat Phase .......................................... 154 Military Assistance ........................................................... 156 Wealth