"I informed John Bolton last night that his services are no longer needed at the White House. I disagreed strongly with many of his suggestions..."

"... as did others in the Administration, and therefore I asked John for his resignation, which was given to me this morning. I thank John very much for his service. I will be naming a new National Security Advisor next week."

Said President Trump, quoted in "Trump Fires John Bolton as National Security Adviser" (NYT).

His departure comes as Mr. Trump is pursuing diplomatic openings with two of the United States’ most intractable enemies, efforts that have troubled hard-liners in the administration, like Mr. Bolton, who view North Korea and Iran as profoundly untrustworthy.

The president has continued to court Kim Jong-un, the repressive leader of North Korea, despite Mr. Kim’s refusal to surrender his nuclear program and despite repeated short-range missile tests by the North that have rattled its neighbors. In recent days, Mr. Trump has expressed a willingness to meet with President Hassan Rouhani of Iran under the right circumstances, and even to extend short-term financing to Tehran, although the offer has so far been rebuffed.

To his admirers, Mr. Bolton was supposed to be a check on what they feared would be naïve diplomacy, a cleareyed realist who would keep a president without prior experience in foreign affairs from giving away the store to wily adversaries. But Mr. Trump has long complained privately that Mr. Bolton was too willing to get the United States into another war....