Significant U.S. Conflicts

Updated March 17, 2017 | Factmonster Staff

During the first phase of its history, the United States tried to isolate itself from foreign conflicts. In the 1900s, however, the United States participated in two world wars, became a global superpower, and eventually became a major proponent of world trade.


The United States wins theSpanish-American Warand acquiresforeign territories?Puerto Rico,Guam, andThe Philippines.


World War Ibegins.


The U.S. abandonsneutralitytojoin the Alliesin world War I.


World War I ends.


The Senate rejects theTreaty of Versaillesand American membership in theLeague of Nations.


The U.S. declares the war withGermanyto be at and end.


Germany invadesPolandandWorld War IIbegins.


Japanese forces assailPearl Harbor. The U.S. declares war on theAxis Powersandenters World War II.


End of World War II. The U.S. is a founding member of theUnited Nations.


The end of World War II marks the beginning of theCold War. Fearing the spread ofCommunismin war-torn Western Europe, the United States inaugurates theMarshall Plan.


The U.S. and 11 other nations sign the North Atlantic Treaty, formingNATO.


CommunistNorth KoreainvadesSouth Korea. PresidentTrumansends American troops to defend South Korea. The U.S. goes on to lead forces from 15 other nations in theKorean War(1950?1953).


The U.S. Senate passes theGulf of Tonkin Resolutionat the request of PresidentJohnson. The Resolution approvesU.S. militaryinvolvement in theVietnam conflict.


PresidentNixonorders a halt to offensive operations in NorthVietnamon Jan. 15 and representatives from all sides sign a peace pact, ending the longest war in U.S. history. The last American troops depart by March 1973.


PresidentReaganorders an invasion ofGrenadato establish order on the island and eliminate theCubanmilitary presence there. A U.S. peace-keeping force remains until 1985.


TheBerlin Wallcomes down, marking the end of the Cold War.


PresidentBushsends troops toPanamato depose and captureManuel Noriega, who had been indicted for drug trafficking.


Persian Gulf War?the U.S. leads a coalition of 32 countries to driveIraqout ofKuwait, which it had invaded.


U.S.,Canada, andMexicoratify theNAFTAfree-trade agreement.

1993 Somalia

A U.S.-led multinational force attempts to restore order to war-tornSomaliaso that food can be delivered and distributed within the famine-stricken country.

1994 Haiti

AfterHaiti'sdemocratically elected presidentJean-Bertrand Aristideis ousted in a coup in 1991, a U.S. invasion three years later restores him to power.

1994?1995 Bosnia

During the Bosnian civil war, which begins shortly after the country declares independence in 1992, the U.S. launches air strikes onBosniato preventethnic cleansing. It becomes a part ofNATO'speacekeeping force in the region.


The U.S. is a founding member of theWorld Trade Organization (WTO), formed to monitor and promote world trade.

1999 Kosovo

Yugoslavia's province ofKosovo erupts in warin the spring of 1999. AU.S.-led NATO forceintervenes with air strikesafterSlobodan Milosevic'sSerbian forces uproot the population and embark on a plan ofethnic cleansingof Kosovo's ethnic Albanian population.


After theSeptember 11, 2001, terrorist attacks, the U.S. declares war onterrorism.


Operation Enduring Freedom?the U.S. invadesAfghanistanand deposes theTaliban, who had sheltered terrorist leaderOsama bin Laden.


The U.S. launchesOperation Iraqi Freedom, an invasion ofIraq, as part of the war on terrorism.


On Aug. 31, President Obama announces the end of U.S. combat missions in Iraq.


Operation New Dawn begins on Sep. 1. A U.S. transitional troop force will remain in Iraq, tasked with the mission: "advising and assisting Iraq's Security Forces, supporting Iraqi troops in targeted counterterrorism missions, and protecting our civilians."


On May 2, 2011 (May 1 in the U.S.), U.S. troops and CIA operatives shot and killed Osama bin Laden in Abbottabad, Pakistan.


May 1, 2012, President Obama and President Karzai signed theEnduring Strategic Partnership Agreement between the Islamic Republic of Afghanistan and the United States of America. The Agreement provides for the possibility of U.S. forces in Afghanistan after 2014, for the purposes of training Afghan Forces and targeting the remnants of al-Qaeda. Afghanistan will be a ?Major Non-NATO Ally? and as such, the U.S. will support the training, equipping, advising and sustaining of Afghan National Security Forces, and social and economic assistance.

Reacting to instability due to Syria's civil war, the U.S. sends troops to neighboring Jordan--to contain the border; and Turkey--to prevent any Syrian-based missile strikes.


According to the Department of Defense, 6,097 targets were damaged or destroyed as of April 23, 2015. The strikes were conducted as part of Operation Inherent Resolve, an undertaking meant to eliminate the Islamic State of Irag and the Levant (ISIL) terrorist group and the threat they pose to Iraq, Syria, the region, and the wider international community. Coalition nations conducting airstrikes in Iraq include the United States, Australia, Belgium, Canada, Denmark, France, Jordan, the Netherlands and the United Kingdom; coalition nations conducting airstrikes in Syria include the United States, Bahrain, Canada, Jordan, Saudi Arabia and the United Arab Emirates.