US Department of Defense | United States government

U.S. Department of Defense, executive division of the U.S. federal government responsible for ensuring national security and supervising U.S. military ... U.S.DepartmentofDefense Sections&Media Article Introduction FastFacts Facts&RelatedContent Media Images AdditionalInfo MoreArticlesOnThisTopic Contributors ArticleHistory Home Politics,Law&Government Politics&PoliticalSystems U.S.DepartmentofDefense UnitedStatesgovernment Alternatetitles:DOD Print Cite verifiedCite Whileeveryefforthasbeenmadetofollowcitationstylerules,theremaybesomediscrepancies. Pleaserefertotheappropriatestylemanualorothersourcesifyouhaveanyquestions. SelectCitationStyle MLA APA ChicagoManualofStyle CopyCitation Share Share Sharetosocialmedia Facebook Twitter URL https://www.britannica.com/topic/US-Department-of-Defense More GiveFeedback ExternalWebsites Feedback Corrections?Updates?Omissions?Letusknowifyouhavesuggestionstoimprovethisarticle(requireslogin). 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ExternalWebsites OfficialSiteoftheUnitedStatesDepartmentofDefense By TheEditorsofEncyclopaediaBritannica | ViewEditHistory thePentagon Seeallmedia Date: 1947-present ...(Showmore) AreasOfInvolvement: defense nationalsecurity ...(Showmore) RelatedPeople: JamesMattis RobertM.Gates DonaldRumsfeld DanielEllsberg MichaelGriffin ...(Showmore) Seeallrelatedcontent→ U.S.DepartmentofDefense,executivedivisionoftheU.S.federalgovernmentresponsibleforensuringnationalsecurityandsupervisingU.S.militaryforces.BasedinthePentagon,itincludestheJointChiefsofStaff,thedepartmentsoftheU.S.Army,U.S.Navy,andU.S.AirForce,andnumerousdefenseagenciesandalliedservices.Itwasformedin1947byanactofCongress(amended1949)combiningtheWarandNavyDepartments.ThemissionoftheDepartmentofDefenseistoprovide,throughitsmilitarystrength,asolidfoundationforthenationalpolicyoftheUnitedStates.TheforerunneroftheDepartmentofDefense,theNationalMilitaryEstablishment,wascreatedbytheNationalSecurityActof1947andevolvedfromtheexperiencesofWorldWarII.WhilecombatandservicecomponentsoftheDepartmentsoftheArmyandtheNavyfoughttogetherinvarioustheatresofoperationunderunifieddirectionofoverseascommanders,theindividualmilitarydepartmentsreportedseparatelytothepresident.Theconflictingandcompetitivepoliciesofthesedepartmentspreventedatrulyeffective,coordinated,andunifiedmilitaryeffort.Toovercomethisorganizationaldeficiency,theNationalMilitaryEstablishmentwascreated,andthecabinetpostofsecretaryofdefensewasestablishedtoprovideoverallpolicyanddirectionofthemilitarydepartmentswithoutdestroyingtheirindividualidentities.Concurrently,theAirForcewascreatedasathirdmilitarydepartmentonacoequalbasiswiththeDepartmentsoftheArmyandtheNavy.TheoriginalNationalSecurityActof1947providedthesecretaryofdefensewithlimitedauthorityandstafftoexercisecontrol.However,subsequentamendmentstothebasicactin1949,1953,and1958greatlystrengthenedtheauthorityandabilityofthesecretarytodirectdefensepolicy.Withthe1949amendment,themodernDepartmentofDefensewasestablished.Intheearly21stcenturytheDepartmentofDefenseconsistedofthesecretaryofdefense;thedeputysecretaryofdefense;undersecretariesandassistantsecretariesholdingvariousportfolios;theofficeoftheinspectorgeneral;theDepartmentsoftheArmy,Navy,andAirForce;andnumerousdefenseagenciesandfieldactivityoffices.Thesecivilianofficialsandtheirsubordinatesrepresentthepolicy,research,analysis,andresource-managementstaffofthesecretaryofdefense.NationalSecurityActof1947U.S.Pres.HarryS.TrumansigningtheNationalSecurityActof1947.EncyclopædiaBritannica,Inc.Theciviliansecretariesofthemilitarydepartments(Army,Navy,andAirForce)areresponsiblefortheadministrationoftheirparticulardepartmentsandareresponsiblefortraining,equipping,andprovidingcombat-readyforcestothecombatcommands.ThecombatforcesoftheArmy,Navy,AirForce,andMarineCorpsareunderunifiedcombatcommands,organizedoneitherageographicorafunctionalbasis.Aunifiedcommandcontainscombatforcesfrommorethanoneservice,suchasCentralCommand(CENTCOM),whichiscomposedofallArmy,Navy,AirForce,andMarineCorpsunitsinCentralandSouthernAsiaandtheMiddleEast,orSpecialOperationsCommand(USSOCOM),whichoverseesspecialoperationswarfare.TommyFranksandDonaldRumsfeldGen.TommyFranks(left),commanderinchiefofCentralCommand,withU.S.SecretaryofDefenseDonaldRumsfeld,2002.RobertD.Ward—U.S.DepartmentofDefenseThecommandersoftheunifiedcommandsareresponsibletothepresidentandthesecretaryofdefense.Bysecretarialdelegation,theJointChiefsofStaffexerciseoperationaldirectionovertheunifiedcommands.TheJointChiefsofStaffaretheprincipalmilitaryadviserstothepresident,theNationalSecurityCouncil,andthesecretaryofdefense.TheJointChiefsofStaffconsistofthechairman,JointChiefsofStaff,whoisthenation’shighest-rankingmilitaryofficer;thevicechairman;thechiefofstaff,UnitedStatesArmy;thechiefofnavaloperations;thechiefofstaff,U.S.AirForce;thecommandantoftheMarineCorps;andthechiefoftheNationalGuard.Thechiefsareappointedbythepresidenttofour-yearterms.TheJointChiefsofStaffaresupportedbytheJointStaff,whichislimitedbylawtonotmorethan400officers.Thisstaffisorganizedalongconventionalmilitarystafflines,andperformssuchfunctionsasdevelopingstrategicconceptsandwarplans,reviewingtheoperatingplansoftheunifiedcommands,andestablishingunifieddoctrineforoperations.AnassignmenttotheJointStaffprovidesmilitaryofficersauniqueopportunitytoworkoncoordinatedplansandtodevelopanunderstandingoftheintegratedeffortrequiredunderthemodernconceptofjointoperations.JointChiefsofStaffPres.BarackObama(hisbacktothecamera)holdingameetingwiththeJointChiefsofStaffintheOvalOfficeconcerningtherepealof"Don'tAsk,Don'tTell,"November29,2010.PeteSouza—OfficialWhiteHousePhotoIntheearly21stcenturytherewere20defenseagencieswithintheDepartmentofDefense.Theseagencieswereestablishedtoprovideintegratedandunifiedeffortinsupportactivitiesthatgenerallycutacrossservicelines.Thedefenseagencieshaveconsolidatedfunctionsthatwerepreviouslyfractionalizedamongthemilitaryservices.AmongtheseagenciesweretheNationalSecurityAgency(NSA),whichheldresponsibilityforsignalsintelligenceandcryptography;theDefenseAdvancedResearchProjectsAgency(DARPA),responsibleformilitaryresearchanddevelopment;theDefenseIntelligenceAgency(DIA),responsibleformilitaryintelligence;andtheNationalReconnaissanceOffice,whichdesignsandmaintainsreconnaissancesatellitesforusebytheDepartmentofDefenseandtheintelligencecommunity.NationalSecurityAgencyNationalSecurityAgencyheadquarters,FortMeade,Maryland.TrevorPaglenNationalReconnaissanceOfficeNationalReconnaissanceOfficeheadquartersinChantilly,Virginia.TrevorPaglenTheneedforthemilitarytoconsiderimplicationsofpolitical, economic,andscientificfactorsinthedevelopmentofmilitary plansandmilitaryadvicerequiresthatseniormilitaryofficers haveabroadeducationinthesedisciplines.Tothisend,the militarydepartmentshaveestablishedanextensivecontinuingeducation systemfortheirofficers.Includedinthiseducationalsystemarejoint-serviceschoolssuchastheJointForcesStaffCollegeandNationalDefenseUniversity,aswellasindividualserviceschoolssuchastheNavalWarCollege,AirUniversity,andArmyWarCollege.Theseschoolsoffergraduateschool-levelprogramstotrainfuturemilitaryleadersasbroadlyeducatedofficerswhounderstandtheimportanceofpolitical,economic,andscientificfactorsonmilitaryplanning.TheDepartmentoftheArmy,throughitsCorpsofEngineers,alsoperformsimportantcivilfunctionsinimprovingrivers,harbours,andwaterwaysfornavigation,inconstructingflood-controlandsimilarprojectsinvariouspartsofthecountry,andinadministeringthelawsgoverningnavigablewaters.U.S.ArmyCorpsofEngineersTheU.S.ArmyCorpsofEngineersopenedthefloodgatesontheBonnetCarreSpillwaynearNewOrleansinMay2011tomanagetheflowoftheMississippiRiver.U.S.GeologicalSurvey ThisarticlewasmostrecentlyrevisedandupdatedbyMichaelRay.