John Bolton, a noted foreign policy hawk, will replace H.R. McMaster as President Donald Trump's national security advisor, the latest move in an ongoing shakeup of the president's top advisors.
In a tweet Thursday, Trump said Bolton, a former U.S. ambassador to the U.N., will take over the post on April 9. McMaster, an Army lieutenant general, "has done an outstanding job & will always remain my friend," the president wrote.
In Bolton, who served as U.N. ambassador for parts of 2005 and 2006, Trump will get an advisor whom experts consider more in favor of military intervention around the globe than McMaster is. For instance, in February, he made the legal case in The Wall Street Journal for a pre-emptive strike on North Korea. In 2015 he wrote an op-ed for The New York Times titled "To Stop Iran's Bomb, Bomb Iran."
In a separate statement, McMaster said he is requesting retirement from the Army this summer, after which he will "leave public service." As recently as last week, the White House denied a string of reports saying McMaster could soon leave.
McMaster's exit is just the latest departure of a top Trump administration official announced in the last two weeks. Larry Kudlow recently replaced Gary Cohn as director of the National Economic Council, while Mike Pompeo is set to replace Rex Tillerson as secretary of State, pending Senate confirmation.
Along with Cohn and Tillerson, McMaster was considered a more moderate voice in the White House who restrained the president's impulses. Bolton, 69, has not only taken a hawkish stance on North Korea but also advocated for scrapping the Iran nuclear deal. He served more than one stint in the State Department and was a fellow at the American Enterprise Institute.
In an interview with Fox News on Thursday night, Bolton said the personal views he has expressed in the past are "behind me now."
McMaster will become the second national security advisor to leave the job since Trump took office last year. He had the task of advising a president who often tweets unfiltered thoughts about delicate national security situations such as North Korea's weapons program and the Iran nuclear deal.
Since taking the position, McMaster has faced criticism from some Trump supporters who have attacked him as a "globalist." McMaster drew Trump's ire last month by saying the evidence that Russia meddled in the 2016 U.S. election is "incontrovertible," following more than a dozen indictments from special counsel Robert Mueller's office. Trump lashed out at McMaster in a late-night Twitter post last month.
"General McMaster forgot to say that the results of the 2016 election were not impacted or changed by the Russians and that the only Collusion was between Russia and Crooked H, the DNC and the Dems. Remember the Dirty Dossier, Uranium, Speeches, Emails and the Podesta Company!" Trump wrote.
Foreign policy observers said Bolton taking over for McMaster will have immediate implications for policy toward both Iran and North Korea. The move is "bad news for those who were hoping the Iran deal would somehow survive," said Harry Kazianis, director of defense studies at the Center for the National Interest.
Ian Bremmer, president of political risk consultancy firm Eurasia Group, tweeted that Bolton's hire makes the proposed meeting between Trump and North Korean dictator Kim Jong Un "far riskier."
Bolton's hiring, combined with Trump's tariffs against China that rattled financial markets Thursday, marks "probably the worst/biggest single day for geopolitical risk" since Eurasia Group's founding in 1998, Bremmer wrote.
CNBC's Amanda Macias contributed to this article.