John Bolton is an American attorney, political commentator, Republican consultant, former diplomat and national security advisor. He was appointed as the 27th United States National Security Advisor by President Donald Trump and served in that capacity for less than one-and-a-half year before being fired. He was previously named the interim United States Ambassador to the United Nations by President George W. Bush, despite having ridiculed the institution several times in the past. He also worked with the administrations of Ronald Reagan and George H.W. Bush. He was actively involved in making sure that America invaded Iraq following the September 2001 terrorist attacks, called for preemptive attacks on North Korea, and advocated regime change in nations like Syria, Libya, Iran, Cuba, Venezuela, Yemen and North Korea. He recently became the central figure in the Senate impeachment trial of Trump after excerpts from his upcoming memoir got leaked, calling for him to appear as a witness.