By Nicole Gaouette, CNN

President Donald Trump's decision to jettison John Bolton -- his third national security adviser since January 2017 -- was both shocking and typical for a President who has generated unprecedented churn among his national security team.

Since his inauguration, the President has plowed through a secretary of state, a defense secretary and an attorney general. He's worked his way through an FBI chief, a director of national intelligence, a homeland security secretary, two White House chiefs of staff and five deputy national security advisers. He's seen an ambassador to the UN come and go, as well as a Mideast peace negotiator.

Enough senior-level national security experts and appointees have exited the Trump administration's State Department and National Security Council to field two baseball teams with players left over to warm the bench.

Many resigned under pressure. Some, like Brett McGurk, Trump's envoy to the global coalition against ISIS, left in protest.

'A mess?'

The rapidly spinning revolving door left administration officials facing unusually frank questions Tuesday about the coherence and continuity of the administration's foreign policy.

"Is this national security team a mess?" CNN's Jim Acosta asked Treasury Secretary Steven Mnuchin, who held a news conference Tuesday to announce new counterterrorism designations with Secretary of State Mike Pompeo.

"Absolutely not," Mnuchin protested. "That's the most ridiculous question I've ever heard of."

But in a moment that spoke volumes about dissent and hostility within Trump's national security team, both men, asked if they had been blindsided by Bolton's departure, grinned hugely before launching into their answers.

Trump ousted his national security adviser as the US faces a slew of challenges: tensions with Iran, North Korea's ongoing missile tests, China's assertiveness in Asian waters and Russia's ongoing aggression in Ukraine and Crimea, as well as its election interference in the US and across Europe. It comes just days after the President rescinded an offer to the Taliban to visit Camp David, leaving his path on Afghanistan unclear.

Bolton's departure also comes just two weeks before the UN General Assembly -- known as the Super Bowl of diplomacy -- leaving the President a man down before he and his senior national security team arrive to face off against adversaries and cajole allies. (His new ambassador to the UN, Kelly Craft, was scheduled to be sworn in Tuesday and won't be prepared to play a major role, sources say.)

The UN event could highlight divisions on issues like climate change and the Iran nuclear deal with longtime US partners, many of whom have experienced the unsettled nature of Trump's national security infrastructure in the form of ambassador vacancies.

"John Bolton's sudden departure is a symbol of the disarray that has unnerved our allies since day one of the Trump Administration," House Speaker Nancy Pelosi said on Twitter. "Steady leadership & strategic foreign policy is key to ensuring America's national security."

'Dysfunctional'

Just an hour before Pompeo and Mnuchin spoke, the White House press office had been advising reporters that Bolton would appear alongside them. And it was clear there will be a battle over the narrative of Bolton's exit, as he claimed he resigned, while Trump insisted he had fired the longtime Washington operative.

"This is a thoroughly dysfunctional operation," said a Democratic senior foreign policy source. "It is important to reflect on the fact that Pompeo is the last person standing. Everyone else -- McMaster, Mattis, Coats, Tillerson, John Kelly, Kirstjen Nielsen -- found it impossible to work with Trump and are bitter about their experience," the source said, listing a national security adviser, defense secretary, director of national intelligence, secretary of state, White House chief of staff and a homeland security secretary.

Pompeo, who started out as Trump's CIA director in January 2017, said world leaders should not expect any foreign policy changes in Bolton's absence. "These have been the President's policies," Pompeo said, noting that his advisers "give him our best wisdom," as well as advice and data to make decisions.

"I don't think any leader around the world should make any assumption the President's foreign policy will change in any material way," he said.

Pompeo fended off questions about Trump's decision.

"The President's entitled to the staff that he wants," the top US diplomat said, adding that Trump deserves staff who he "trusts" and "values" and "whose efforts and judgment benefit national security."

He acknowledged that he had disagreed with Bolton "many times."

"That's for sure," he said, but added that he disagrees with others as well.

Pompeo continued, "We work very closely with the President," adding that they "have a good understanding of how he's thinking about things."

Below is a partial list of senior national security officials in the Trump administration who have resigned or been pushed out and the timing of their departures:

Michael Flynn -- National security adviser -- February 2017

K.T. McFarland -- Deputy national security adviser -- May 2017

James Comey -- FBI director -- May 2017

Reince Priebus -- White House chief of staff -- July 2017

Dina Powell -- Deputy national security adviser -- January 2018

Rex Tillerson -- Secretary of state -- March 2018

H.R. McMaster -- National security adviser -- April 2018

Andrew McCabe -- Deputy director of the FBI -- March 2018

Mira Ricardel -- Deputy national security adviser -- November 2018

Jeff Sessions -- Attorney general -- November 2018

Nikki Haley -- US ambassador to the UN -- December 2018

James Mattis -- Secretary of defense -- December 2018

Brett McGurk -- Special presidential envoy to the global coalition to defeat ISIS -- December 2018

John Kelly -- White House chief of staff -- January 2019

Kirstjen Nielsen -- Homeland security secretary -- April 2019

Dan Coats -- Director of national intelligence -- August 2019

Sue Gordon -- Deputy director of national intelligence -- August 2019

Jason Greenblatt -- Representative for international negotiations with Israel and the Palestinians -- September 2019


Notable White House and National Security Council departures:

Robin Townley -- Senior director for Africa -- February 2017

Derek Harvey -- Senior director for Middle East and North Africa -- July 2017

Ezra Cohen-Watnick -- Senior director for intelligence programs -- August 2017

Tom Bossert -- Assistant to the President for Homeland Security and Counterterrorism -- April 2018

Michael Barry - Senior director for intelligence programs -- July 2018

Kirsten Fontenrose -- Director for the Persian Gulf -- November 2018

Fiona Hill - Senior director for European and Russian Affairs on the National Security Council -- August 2019

Notable State Department departures:

Tom Shannon -- Under Secretary of State for Political Affairs -- February 2018

Susan Thornton -- Assistant Secretary of State for East Asian and Pacific Affairs -- July 2018

A. Wess Mitchell -- Assistant Secretary of State for European and Eurasian Affairs -- February 2019

Kimberly Breier -- Assistant Secretary of State for Western Hemisphere Affairs -- August 2019