U.S. President Donald Trump's choice of John Bolton to replace Army Lieutenant General H.R. McMaster as national security advisor replaces a restraining influence in the president's inner circle with a dedicated hawk.
Bolton is known as a colorful figure in Washington and an inveterate bureaucratic infighter. On his desk at the State Department during the administration of former Republican President George W. Bush, he kept a defused hand grenade.
In 2003, on the eve of six-nation talks over Pyongyang's nuclear program, he lambasted then North Korean leader Kim Jong Il in a speech in Seoul, calling him a "tyrannical dictator."
North Korea responded by calling Bolton "human scum."
Like Trump, Bolton did not serve in the Vietnam War, instead joining the Army National Guard.
Bolton's sometimes abrasive style got him into trouble in the Bush administration. One incident that came back to haunt him was his reported dressing-down of an intelligence analyst who questioned him over whether Cuba had an advanced chemical and biological weapons program.
During his 2005 confirmation hearing to become U.N. ambassador, State Department intelligence chief Carl Ford called Bolton "a serial abuser" and "a quintessential kiss-up, kick-down sort of guy."
The Senate never approved Bolton's nomination. Bush instead appointed him to the U.N. post for 17 months under a process known as a recess appointment that bypasses confirmation.
In a Fox News interview on Thursday evening, after news of his appointment broke, Bolton appeared to temper his often harsh rhetoric. "Frankly, what I have said in private now, is behind me, at least effective April 9," he said, referring to the date he is scheduled to take over from McMaster.