'It is the president' who decides on going to war, regardless of John Bolton’s rhetoric: National security expert

John Bolton's views are 'a little bit extreme," said a former Bush official.

But, Hadley said, "It is the president that makes those decisions."

"He's working for the president," said Mullen, a former chairman of the Joint Chiefs of Staff under both presidents Bush and Obama. "The president is clearly not going to be working for him. So it's going to be the president's views that I think Mr. Bolton will actually in the end execute."

However, Mullen said, if Bolton’s past rhetoric were taken at face value, he’d have concerns.

Mullen added, "I wonder, you know, are we going backwards in terms of those countries ... the ones that still present huge challenges for us" such as Iran and North Korea, and will Bolton lead to "a much more militaristic" approach.

Hadley said he doesn't agree with some of Bolton's stated views, but added that tough rhetoric from President Trump may have led to progress on North Korea by getting China involved.

Hadley also said of Bolton, “John is a very smart, very experienced, very tough guy," adding that the president deserves a national security adviser he is comfortable with.

“The president is the person elected by the American people to set foreign policy,” Hadley said. “He deserves people around him who think the same way.”