Michael Flynn: Former US national security adviser
Michael Flynn's remarkable appointment as Donald Trump's national security adviser ended in controversy when he resigned over contacts he had made with Russia before Mr Trump was in office.
Mr Flynn was all but written off two years ago when he was removed from his post as a Pentagon intelligence chief.
But the retired US Army three-star lieutenant-general was one of Donald Trump's closest advisers and most ardent supporters during the campaign.
His importance was underlined just days before his resignation, when he was with the president at his Mar-A-Lago estate in Florida as he hosted his first foreign leader there, Japanese Prime Minister Shinzo Abe.
In the past, Mr Flynn has complained he was fired from the Defence Intelligence Agency (DIA) in 2014 after just two years for telling hard truths about the war on Islamist extremism.
Mr Flynn believes the US is losing a global war against Islamist extremism that may last for generations.
But insiders have suggested his exit at the DIA may have been related to his unpopular overhaul of the agency.
Former US officials who worked closely with him described him as extremely smart, though a poor manager.
Indeed, Mr Flynn, a father-of-two who married his high school sweetheart, went on to become one of the previous administration's most outspoken critics, all the more surprising as he was a life-long Democrat.
But the Rhode Islander said he no longer recognised the Democrats as the party he once supported.
He instead decided to align himself with Mr Trump, a man whom he rates as a hustler and outsider like himself, part of a larger fight against "the dishonesty and deceit of our government".
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Mr Flynn was an almost evangelical supporter of Mr Trump.
"We just went through a revolution," he said after the businessman's shock election victory.
"This is probably the biggest election in our nation's history, since bringing on George Washington when he decided not to be a king. That's how important this is."
Mr Flynn and Mr Trump share many views, including the advantages of closer ties with Russia, renegotiating the Iran deal and combating the threat from Islamic State militants.
Like Mr Trump, Mr Flynn has called the 2003 invasion of Iraq a strategic blunder.
Even the areas where the two disagreed at first were quickly smoothed over.
Gen Flynn's declaration that he was pro-choice was quickly amended to pro-life in July, after it sparked outrage among Trump supporters.
And, like Mr Trump, he is no stranger to controversy.
Back during his days at the DIA, he apologised for a presentation which suggested make-up made women "more attractive" and encouraged people to dress for their body shape.
He later said neither he nor the agency "condone this briefing".
Last year, his appearance at a banquet held in honour of the Russian government, where Gen Flynn sat two seats away from Vladimir Putin, raised eyebrows, with his apparent warmth towards Moscow concerning some national security experts.
More controversial yet have been his views on Islam.
In February 2016, he tweeted "fear of Muslims is RATIONAL", while in July, he told the New York Post "the Islamic world is an epic failure" as he advocated his plan to beat radicalism.
In August, he spoke at an event in Dallas, Texas, for an anti-Islamist group Act for America, saying that Islam "is a political ideology" and that it "definitely hides behind being a religion".
Some expressed concern at how much influence Mr Flynn could wield over a president with little international experience.
"I would be worried about an impulsive president with an impulsive security adviser," Representative Adam Schiff, the senior Democrat on the House intelligence committee, told CNN.
But for all his critics, there were those who stood behind Mr Flynn, a man who built a reputation as an astute intelligence professional during his three decades in the US Army.
David Deptula, a retired air force lieutenant general who used to work with him, praised his willingness to "speak truth to power and not politicise his answers".
"Mike Flynn is a straight shooter. And that's exactly what we need in terms of senior leaders giving advice to the national leadership," Mr Deptula said.
Even before the allegations emerged that he discussed easing of sanctions on Russia, Mr Flynn's tenure had already seen its fair share of controversies.
His son, who previously held a position in the Trump transition team, resigned after he continued tweeting about the #Pizzagate hoax even after a gunman briefly took the Washington restaurant hostage.
One of Mr Flynn's top aides was also denied a critical security clearance by the CIA, exposing tension between the Trump administration and the US intelligence community.