NBCNews.comMullen 'Extremely Concerned' About North Korea SituationNBCNews.comWASHINGTON — Former Chairman of the Joint Chiefs of Staff Ret. Adm. Mike Mullen said he is “extremely concerned” about heightened tensions between North Korea and the United States, and worries that disproportional responses and unintended ...Mullen Expresses Concern Over 'Brinkmanship' With North KoreaNPRMullen: Trump's rhetoric on North Korea 'has taken away options'PoliticoMullen on North Korea: 'It can really get out of control fast'The HillNewsmaxall 7 news articles »