哎呀呀,不太brief.自己随便看看吧.

　　WorldWarII,ortheSecondWorldWar[1](oftenabbreviatedWWIIorWW2),wasaglobalmilitaryconflictwhichinvolvedamajorityoftheworld'snations,includingallofthegreatpowers,[2]organizedintotwoopposingmilitaryalliances:theAlliesandtheAxis.Thewarinvolvedthemobilisationofover100millionmilitarypersonnel,makingitthemostwidespreadwarinhistory.Inastateof"totalwar",themajorparticipantsplacedtheircompleteeconomic,industrial,andscientificcapabilitiesattheserviceofthewareffort,erasingthedistinctionbetweencivilianandmilitaryresources.Overseventymillionpeople,themajorityofwhomwerecivilians,werekilled,makingitthedeadliestconflictinhumanhistory.[3]

　　ThestartofthewarisgenerallyheldtobeinSeptember1st1939withtheGermaninvasionofPolandandsubsequentdeclarationsofwaronNaziGermanybymostofthecountriesintheBritishCommonwealthandFrance.[4][5]Manybelligerentswereatwarbeforeorafterthisdate,duringaperiodwhichspannedfrom1937to1941,asaresultofotherevents.AmongstthesemaineventsaretheMarcoPoloBridgeIncident(foughtbetweenNationalistChinaandJapan),thestartofOperationBarbarossa(theNaziinvasionoftheSovietUnion),andtheattacksonPearlHarborandBritishandDutchcoloniesinSouthEastAsia.

　　Afterthewarendedin1945,theSovietUnionandtheUnitedStatesemergedastheworld'ssuperpowers.ThissetthestagefortheColdWar,whichlastedforthenext45years.TheUnitedNationswasformedinthehopeofpreventinganothersuchconflict.Theacceptanceoftherighttoself-determinationaccelerateddecolonizationmovementsinAsiaandAfrica,whileWesternEuropeitselfbeganmovingtowardintegration.