TheKoreanWar(25June1950–27July1953)[29][a][31]wasawarbetweentheRepublicofKorea(SouthKorea),supportedbytheUnitedNations,andtheDemocraticPeople'sRepublicofKorea(NorthKorea),atonetimesupportedbythePeople'sRepublicofChinaandtheSovietUnion.ItwasprimarilytheresultofthepoliticaldivisionofKoreabyanagreementofthevictoriousAlliesattheconclusionofthePacificWarattheendofWorldWarII.TheKoreanPeninsulawasruledbytheEmpireofJapanfrom1910untiltheendofWorldWarII.FollowingthesurrenderoftheEmpireofJapaninSeptember1945,Americanadministratorsdividedthepeninsulaalongthe38thparallel,withU.S.militaryforcesoccupyingthesouthernhalfandSovietmilitaryforcesoccupyingthenorthernhalf.

　　ThefailuretoholdfreeelectionsthroughouttheKoreanPeninsulain

　　1948deepenedthedivisionbetweenthetwosides;theNorthestablished

　　acommunistgovernment,whiletheSouthestablishedaright-winggovernment.

　　The38thparallelincreasinglybecameapoliticalborderbetweenthe

　　twoKoreanstates.Althoughreunificationnegotiationscontinuedinthe

　　monthsprecedingthewar,tensionintensified.Cross-borderskirmishes

　　andraidsatthe38thparallelpersisted.Thesituationescalatedinto

　　openwarfarewhenNorthKoreanforcesinvadedSouthKoreaon25June

　　1950.In1950,theSovietUnionboycottedtheUnitedNationsSecurityCouncil.

　　IntheabsenceofavetofromtheSovietUnion,theUnitedStatesand

　　othercountriespassedaSecurityCouncilresolutionauthorizing

　　militaryinterventioninKorea.

　　TheU.S.provided88%ofthe341,000internationalsoldierswhich

　　aidedSouthKoreanforces,withtwentyothercountriesoftheUnited

　　Nationsofferingassistance.Sufferingseverecasualtieswithinthe

　　firsttwomonths,thedefenderswerepushedbacktothePusanperimeter.ArapidU.N.counter-offensivethendrovetheNorthKoreanspastthe38thparallelandalmosttotheYaluRiver,whenthePeople'sRepublicofChina(PRC)enteredthewaronthesideofNorthKorea.

　　ChineseinterventionforcedtheSouthern-alliedforcestoretreat

　　behindthe38thparallel.Whilenotdirectlycommittingforcestothe

　　conflict,theSovietUnionprovidedmaterialaidtoboththeNorth

　　KoreanandChinesearmies.Thefightingendedon27July1953,whenthe

　　armisticeagreementwassigned.Theagreementrestoredtheborder

　　betweentheKoreasnearthe38thParallelandcreatedtheKoreanDemilitarizedZone(DMZ),a2.5-mile(4.0km)-widefortifiedbufferzonebetweenthetwoKoreannations.Minorincidentsstillcontinuetoday.

　　Fromamilitaryscienceperspective,theKoreanWarcombinedstrategiesandtacticsofWorldWarIandWorldWarII:itbeganwithamobilecampaignofswiftinfantryattacksfollowedbyairbombingraids,butbecameastatictrenchwarbyJuly1951.

　　MaoZedong'sdecisiontoconfronttheUnitedStatesintheKoreanWar

　　wasadirectattempttoconfrontwhattheCommunistblocviewedasthe

　　mostpowerfulanti-Communistpowerintheworld,undertakenatatime

　　whentheChineseCommunistregimewasstillconsolidatingitsownpower

　　afterwinningtheChineseCivilWar.

　　Maoprimari