John Bolton to replace H.R. McMaster as White House national security adviser, Trump says 3/23/2018 1:49:18 AM Former UN ambassador John Bolton (L) will be replacing H.R. McMaster as U.S. national security adviser on April 9,2018. Fox News, March 23, 2018  - President Trump announced Thursday that former  United Nations  Amb. John Bolton will replace Gen. H.R. McMaster as his National Security Adviser effective April 9 -- the latest in a growing list of White House staff shakeups over the past year. “I am pleased to announce that, effective 4/9/18, Amb. John Bolton will be my new National Security Advisor. I am very thankful for the service of General H.R. McMaster who has done an outstanding job & will always remain my friend. There will be an official contact handover on 4/9,” Trump tweeted. The president’s announcement came after months of speculation over whether McMaster would resign or be fired from his post. Bolton told Fox News' “The ...