Instances of Use of United States Armed Forces Abroad, 1798-2018
Released: 2018-12-28T00:00:00

Introduction

The following list reviews hundreds of instances in which the United States has used military forces abroad in situations of military conflict or potential conflict to protect U.S. citizens or promote U.S. interests. The list does not include covert actions or numerous occurrences in which U.S. forces have been stationed abroad since World War II in occupation forces or for participation in mutual security organizations, base agreements, or routine military assistance or training operations. Because of differing judgments over the actions to be included, other lists may include more or fewer instances.

These cases vary greatly in size of operation, legal authorization, and significance. The number of troops involved ranges from a few sailors or marines landed to protect American lives and property to hundreds of thousands in Korea and Vietnam and millions in World War II. Some actions were of short duration, and some lasted a number of years. In some examples, a military officer acted without authorization; some actions were conducted solely under the President's powers as Chief Executive or Commander in Chief; other instances were authorized by Congress in some fashion. In 11 separate cases (listed in bold-face type ) the United States formally declared war against foreign nations. For most of the instances listed, however, the status of the action under domestic or international law has not been addressed. Most occurrences listed since 1980 are summaries of U.S. military deployments reported to Congress by the President as a result of the War Powers Resolution. Several of these presidential reports are summaries of activities related to an ongoing operation previously reported. Note that inclusion in this list does not connote either legality or level of significance of the instance described. This report covers uses of U.S. military force abroad from 1798 to December 2018. It will be revised as circumstances warrant.

Listing of Notable Deployments of U.S. Military Forces Overseas, 1798-2018

Related CRS Products

CRS In Focus IF10675, Army Security Force Assistance Brigades (SFABs) , by Andrew Feickert.

CRS In Focus IF10534, Defense Primer: President's Constitutional Authority with Regard to the Armed Forces , by Jennifer K. Elsea.

CRS In Focus IF10535, Defense Primer: Congress's Constitutional Authority with Regard to the Armed Forces , by Jennifer K. Elsea.

CRS In Focus IF10539, Defense Primer: Legal Authorities for the Use of Military Forces , by Jennifer K. Elsea.

CRS In Focus IF10165, South Korea: Background and U.S. Relations , by Mark E. Manyin, Emma Chanlett-Avery, and Brock R. Williams.

CRS Insight IN10797, Attack on U.S. Soldiers in Niger: Context and Issues for Congress , by Alexis Arieff.

CRS Report R44853, Additional Troops for Afghanistan? Considerations for Congress , by Kathleen J. McInnis and Andrew Feickert.

CRS Report RL30588, Afghanistan: Post-Taliban Governance, Security, and U.S. Policy , by Kenneth Katzman.

CRS Report R43344, Conflict in South Sudan and the Challenges Ahead , by Lauren Ploch Blanchard.

CRS Report R41989, Congressional Authority to Limit Military Operations , by Jennifer K. Elsea, Michael John Garcia, and Thomas J. Nicola.

CRS Report R43377, The Central African Republic: Background and U.S. Policy , by Alexis Arieff and Tomas F. Husted.

CRS Report RL31133, Declarations of War and Authorizations for the Use of Military Force: Historical Background and Legal Implications , by Jennifer K. Elsea and Matthew C. Weed.

CRS Report R42699, The War Powers Resolution: Concepts and Practice , by Matthew C. Weed.

CRS Report R43612, The Islamic State and U.S. Policy , by Christopher M. Blanchard and Carla E. Humud.

CRS Report R43478, NATO: Response to the Crisis in Ukraine and Security Concerns in Central and Eastern Europe , coordinated by Paul Belkin.

CRS Report RL33460, Ukraine: Current Issues and U.S. Policy , by Vincent L. Morelli.

CRS Report R41481, U.S.-South Korea Relations , coordinated by Mark E. Manyin.

CRS Report R42077, The Unified Command Plan and Combatant Commands: Background and Issues for Congress , by Andrew Feickert.

CRS Report RS21405, U.S. Periods of War and Dates of Recent Conflicts , by Barbara Salazar Torreon.

Sources

In addition to the historical resources listed in the " Introduction ," below are official government websites that serve as authoritative sources of information for this report.

Central Intelligence Agency (CIA), News & Information, Press Releases and Statements https://www.cia.gov/news-information/press-releases-statements

Department of Defense (DOD), News Releases https://dod.defense.gov/News/Releases/

DOD, Secretary of Defense Speeches https://dod.defense.gov/News/Speeches/SECDEF-All-Speeches/

DOD, Transcripts https://dod.defense.gov/News/Transcripts/

DOD, America's Continued Commitment to European Security, Operation Atlantic Resolve https://dod.defense.gov/News/Special-Reports/0218_Atlantic-Resolve/

DOD, Operation Inherent Resolve (OIR), Targeted Operations to Defeat ISIS https://dod.defense.gov/OIR/

DOD, Unified Command Plan, Commanders' Area of Responsibility https://www.defense.gov/know-your-military/combatant-commands/

Department of the Army, Official Army Announcements https://www.army.mil/news/newsreleases

Department of the Navy, Continuing Promise Humanitarian Missions http://www.navy.mil/local/cp/index.asp

Department of State, Bureau of Public Affairs: Office of Press Relations http://www.state.gov/r/pa/prs/

The White House Briefing Room , Briefings and Statements https://www.whitehouse.gov/briefings-statements/