On Thursday, Donald Trump named John R. Bolton as his new national security advisor, replacing Lt Gen H.R. McMaster.
Bolton, who is a former US ambassador to the United Nations, replaced McMaster in the role, who had reportedly clashed with Trump on key issues in recent weeks.
McMaster had been brought into the Trump administration as a successor to Michael Flynn, who was fired for not revealing the full extent of his contacts with Russia.
55-year-old McMaster's departure has been rumoured for weeks and is said to have come to a head after Trump congratulated Vladimir Putin on his victory in the Russian elections, despite being advised not to.
On Thursday, Trump announced the appointment of Bolton as his National Security Advisor on Twitter, and also added that McMaster had done an "outstanding job" and that they will remain friends.
Bolton isn't a stranger to the White House, having served under Ronald Regan and both George W. Bush and George H.W. Bush during his career, in various roles.
Trump and his chief of staff are said to have met with Bolton earlier this month to discuss their policy in regards to North Korea and Iran.
Despite his experience in American politics, a few elements of the 69-year-old's career has gotten people concerned about his recent ascension to power.
Bolton is reported to be an advocate of war, having backed the invasion of Iraq in 2003.
On top of this, he is currently the chairman of the right-wing think tank website Gatestone Institute, which primarily publishes articles about Islam, the Middle East, immigrants and "military and diplomatic threats to the United States".
The website describes itself as:
Gatestone Institute, a non-partisan, not-for-profit international policy council and think tank is dedicated to educating the public about what the mainstream media fails to report.
Bolton has written numerous articles for the website since its inception in 2008. His most recent piece is titled "The Legal Case for Striking North Korea First".
Other recent articles by Bolton have titles reading "How to Defund the U.N." and "Expect America's Tensions with China and Russia to Rise in 2018."
A tweet from journalist Cas Mudde highlighting other controversial articles on the website is now being shared on Twitter after Trump's announcement on Thursday.
The website has been accused of publishing misleading information about Muslims and migrants, and has also published articles by the far-right Dutch politician Geert Wilders and the outspoken Swedish columnist Ingrid Carlqvist.