This study is to analyzeaboutlessons learned from Vietnam'sHistory and collapse of the Republic ofVietnam (South Vietnam). This paper consisted ofthreepartssuch asthehistoryandwaroftheVietnam,the reasonsaboutcollapseoftheSouth Vietnam,and issuesrising from the SocialistRepublicofVietnam.Especially,analysisofthedatawastriedto objectiveanalysisbased on historicalfactsoftheVietnam.Theresultsof thisstudyareasthefollowings. First, history about Vietnam is giving many lessons to the Korean Peninsula. Korea and Vietnam are positioned in the similar geo-politic location.HistoricallessonsaboutVietnam couldbeunderstoodthrough the studyonnationaltitlesofVietnam.Accordingly,itisneededtostudymore deeply on the classification ofdifferences aboutthe South Vietnam,the RepublicofVietnam,theSocialistRepublicofVietnam,Vietminh,and so on,andcontentsrelatednamesofthenationandwars. Second,thereasonsofoccupyingtheSouth Vietnam bythecommunists couldbesummarizedasthefourelementswhich arethecorruption ofher governmentand leaders,theegoism ofherpeoples,theidleand decayof hermilitary forces,and the wrong strategies ofthe United States (US). Thosefourelementsofreasonsmentioned abovesentencewereinteracted and escalated among others.Consequently,the South Vietnam felldown finally even though positive supports from democratic freedom countries suchastheUS,andsoon. Third,theSocialistRepublicofVietnam disregard thePeace Treaty as the wastepaper,occupied South Vietnam,and won in thewars against CambodiaandChina.Nevertheless,militaryvictoryoftheSocialistRepublic ofVietnam hindered hernationaldevelopment,andgavecausesthatthe countryfelldown astheoneofpoorestcountryin theworld.Andso,the Vietnam should havetried changeofhereconomicsystem called DoiMoi policywhichmeansthecapitalsystem. TheColdWarSystem builtaftertheSecondWorldWar,iscloselyrelated with theVietnam War(1955∼1975)and theKorean War(1950∼1953).In thefuture,thewarsintheEastAsiawillbeaffectedmorebythedynamic internationalrelationshipthaninternalproblemsofothertribes. Recently,four superpower countries around the Korean Peninsula are competingamongothersaswellasopposingtheRepublicofKorea(ROK)with North Korea each other.IftheROK leadersand Korean peopleswill begoforward smoothly on thesurging tidesofgeo-politics,theyneed to acceptpreciselythelessonslearnedfrom theVietnam. Especially North Korean leaderswereurged to acceptthemodelofthe Vietnam'sreform andopeningassoonaspossibleafterdeepconsiderations about the lessons learned from the Vietnam which was blocked the nationaldevelopment.