Trump "has had two voices whispering in his ears: the one counseling diplomacy and warning against conflict, the other recommending belligerence", he said.
Famous for his large moustache and ever-present yellow legal pad, the hardline former U.S. ambassador to the United Nations had pushed back against Trump's dramatic, though so far stumbling attempts to negotiate with the Taliban and North Korea's Chairman Kim Jong Un.
Though this summer saw a series of escalations between the US and Iran, Trump himself nixed airstrikes against the country at the last minute.
Trump was irked by reports that he had faced internal pushback from Bolton over his decision to host leaders of the Taliban at Camp David, multiple people familiar with his frustration say.
- June 30, 2019: Bolton visits Mongolia while Trump goes to the Korean Demilitarized Zone for a historic handshake with North Korean leader Kim Jong Un, suggesting a growing divide between Bolton and Trump. The President announced the plans for the meeting were canceled on Saturday.
Pompeo was speaking at an unrelated briefing at the White House and acknowledged that he had often disagreed with Bolton on issues. I know everyone has talked about this for an awfully long time.
Mr Bolton, a leading foreign policy hawk who was Mr Trump's third national security adviser, was widely known to have pressed the President for a harder line on issues such as North Korea.
Pompeo appeared on the White House podium along with U.S. Treasury Steven Mnuchin to discuss an executive order strengthening sanctions to combat terrorism.
Describing his working-class upbringing to the right-wing news site Breitbart, Bolton said that he still followed lessons from his firefighter father.
"Biegun much more like Pompeo understands that the president is the president, that he makes the decisions", said a source close to the White House.
"The President's view of the Iraq war and Ambassador Bolton's were very different", he said.
Flynn's replacement, McMaster, also a lieutenant general, lasted barely a year.
White House spokesman Hogan Gidley said Charles Kupperman, the deputy national security adviser and a former Reagan administration official and defence contracting executive, would fill Bolton's role on an acting basis.
Of all issues, Bolton has said he is proudest of his efforts under both Bush and Trump to disrupt the International Criminal Court, believing it could target Americans and violate United States sovereignty.
Bolton joins a stack of senior officials to have come and gone during the Republican businessman's tumultuous first term in office.
Bolton, who is seen as hardliner, favored an air strike on Iran after a US drone was downed.
Bolton, a former USA ambassador to the United Nations, was brought into this administration after a stint as a commentator on the Fox News Channel, which is generally supportive of President Trump.
New Delhi will wait for the president to announce his next NSA to start building a key relationship from scratch for the fourth time on Trump's watch.