President Donald Trump's national security adviser Lt. Gen. H.R. McMaster will resign and be replaced by John Bolton, the New York Times first reported late Thursday. Sources told the Times that McMaster will retire from the military and that his departure is amicable. Trump later confirmed the news in a tweet, saying Bolton will take over on April 9. Bolton is known for his hard-line views on Iran and North Korea, and previously served as United States ambassador to the United Nations under President George W. Bush.