John Robert Bolton (born November 20, 1948) is an American attorney, political commentator, Republican consultant, and former diplomat who served as the 27th National Security Advisor of the United States from April 9, 2018 to September 10, 2019.President Trump announced on Tuesday that he had fired John R. Bolton, his third national security adviser, amid fundamental disagreements over how to handle major foreign policy challenges like Iran, North Korea and most recently Afghanistan.  “I informed John Bolton last night that his services are no longer needed at the White House,” the president wrote on Twitter. “I disagreed strongly with many of his suggestions, as did others in the Administration, and therefore I asked John for his resignation, which was given to me this morning. I thank John very much for his service.”