President Donald Trump is replacing national security adviser H.R. McMaster with the former U.N. Ambassador John Bolton, injecting a hawkish foreign policy voice into his administration ahead of key decisions on Iran and North Korea. Trump tweeted Thursday that McMaster has done “an outstanding job & will always remain my friend.” He said Bolton will take over April 9. I am pleased to announce that, effective 4/9/18, @AmbJohnBolton will be my new National Security Advisor.