Among others pleased to be rid of Mr. Bolton were Iran’s leaders, who viewed him as an enemy of peace. Hesameddin Ashena, Mr. Rouhani’s top political adviser, tweeted that Mr. Bolton getting sidelined was “a definitive sign that Washington’s maximum pressure on Iran has failed” and that “Iran’s blockade will end.”
A former under secretary of state and ambassador to the United Nations under President George W. Bush, Mr. Bolton, 70, known for his trademark bushy mustache, was tapped as national security adviser in March 2018 after impressing Mr. Trump with his outspoken performances on Fox News.
Mr. Bolton followed two military officers who held the post before him: Michael T. Flynn, a retired lieutenant general who stepped down after 24 days and later pleaded guilty to lying to the F.B.I.; and his successor, Lt. Gen. H. R. McMaster, who never forged a strong connection with the president and was forced out.
Long before Mr. Trump popularized his “America First” slogan, Mr. Bolton termed himself an “Americanist” who prioritized a cold-eyed view of national interests and sovereignty over what they both saw as a starry-eyed fixation on democracy promotion and human rights. They shared a deep skepticism of globalism and multilateralism, a commonality that empowered Mr. Bolton to use his time in the White House to orchestrate the withdrawal of the United States from arms control treaties and other international agreements.
But if Mr. Trump’s original national security team was seen as restraining a mercurial new commander in chief, the president found himself sometimes restraining Mr. Bolton. Behind the scenes, he joked about Mr. Bolton’s penchant for confrontation. “If it was up to John, we’d be in four wars now,” one senior official recalled the president saying.
Mr. Trump also grew disenchanted with Mr. Bolton over the failed effort to push out President Nicolás Maduro of Venezuela. Rather than the easy victory he was led to anticipate, Mr. Trump has found himself bogged down in a conflict over which he has less influence than he had assumed.
Russia was another flash point for the two. While Mr. Trump seeks to woo President Vladimir V. Putin, Mr. Bolton considers Moscow a hostile player. After Mr. Trump last month suggested inviting Russia back into the Group of 7 despite its annexation of Crimea, Mr. Bolton traveled to Ukraine to reassure its leaders of American support against Russian aggression.