John Robert Bolton (born November 20, 1948) is an American lawyer and diplomat. He was the 27th United States National Security Advisor from April 9, 2018 through September 10, 2019. He has served in several Republican administrations. Bolton served as the U.S. ambassador to the United Nations from August 2005 until December 2006 as a recess appointee by President George W. Bush. John Bolton advocated the second war with Iraq. He resigned in December 2006. 