The Trump cabinet is stuffed with appointments that have upset the Washington establishment — but Mike Flynn was the one that had them really reaching for the smelling salts.

James Mattis, Mr Trump’s new Defence Secretary, is the one saddled with the nickname ‘Mad Dog’, yet he’s regarded as sane and reasonable compared with the other ex-general who was given the job of National Security Adviser.

In a bizarre transformation over just a few years, Mike Flynn went from being one of the most respected intelligence officers of a generation to becoming America’s ‘angriest general’ — railing at the ‘inadequacies’ of the Obama administration’s fight against radical Islam in a highly inflammatory manner.

Flynn's resignation came just hours after sources close to the government revealed that the Justice Department had warned the new administration that his links with the Kremlin had put him in a compromising position and left him open to blackmail

Flynn’s role in the Trump cabinet entailed being the president’s top counsellor on security, weighing in on defence and foreign policy matters that affected national safety. Given Mr Trump’s inexperience in this area, 58-year-old Flynn was expected to be particularly influential in the new White House.

He is an ultra-loyal Trump supporter, despite being raised in a family of Irish-Catholic Democrats and being a registered Democrat.

At last year’s Republican National Convention, amid demands that Hillary Clinton be prosecuted for using a private email server while Secretary of State, he was seen by millions on TV shouting: ‘Lock her up! Lock her up! Damn right! Exactly right!’ He told the convention: ‘If I did a tenth of what she did, I’d be in jail today’.

His Kremlin connections raised eyebrows long before Mr Trump made him his top security adviser.

In a book, he described Russian President Vladimir Putin as a ‘thug’ and ‘totalitarian dictator’ who ‘does not have our interests in mind’.

Flynn stepped down just 24 days into the Administration of new president Donald Trump

Y et this did not prevent him from becoming a regular commentator on the Russia Today network, a Russian government-controlled international television channel.

At a Russia Today network dinner in Moscow in 2015, where he gave an address on world affairs, Flynn was seated next to Mr Putin.

He later explained he had been paid for taking part, but brushed aside concerns that he was aiding a Russian propaganda effort. This wasn’t enough to stop senior Democrats in Congress demanding an investigation into Mr Flynn’s Russian connections.

TIMELINE OF FLYNN'S RUSSIA TROUBLES December 29: Obama announces sanctions against Russia over alleged hacks targeting election. Flynn spoke with Russian ambassador Kislyak repeatedly the same day, it was later reported. December 30: Russian President Vladimir Putin says he will not respond to the sanctions, surprising many U.S. officials. Trump praises Putin's decision as 'very smart.' January 13: Trump spokesman Sean Spicer says Flynn had called Kislyak merely to set up a phone call between Trump and Putin January 15: Vice President-elect Mike Pence says in an interview with CBS that Flynn had not discussed santions in the call with Kislyak January 20: Trump inaugurated president January 23: Spicer, now White House spokesman, said Flynn had told him the call to Kislyak covered four topics: a plane crash that killed a Russian military choir; Christmas greetings; Russian-led talks over the Syrian civil war; and logistics for a call between Putin and Trump January 20-30 (exact date unclear): Acting Attorney General Sally Yates briefs Trump officials that intercepted communications indicated Flynn had discussed sanctions with Kislyak in ways she believed were 'highly significant' and 'potentially illegal' January 30: Trump fires Yates for refusing to defend executive immigration order in court February 8: Flynn denies in interviews that he discussed sanctions in the calls with Kislyak February 9: Flynn backpedals, saying through a spokesperson that he 'couldn't be certain' sanctions weren't discussed February 13: Report breaks of Justice Department concerns about blackmail, and Flynn resigns hours later Advertisement

However, it is Flynn’s outspoken comments on Islam that have drawn most public attention to him in recent years. They came towards the end of a highly distinguished military career, which included stints in both Iraq and Afghanistan, where he was top intelligence officer for the commander of the American-led coalition in 2009-10.

Only after his appointment to head the Defence Intelligence Agency (DIA) in 2011 did things start to fall apart. He became increasingly upset at what he saw as the Obama administration’s failure to confront ISIS and was eventually sacked in 2014.

Critics say he clashed with his bosses because of his chaotic management style and aggressive vision for the agency, and he was allegedly so prone to making dubious assertions his staff dubbed the phenomenon ‘Flynn facts’.

But Flynn insists he was fired because he dared to challenge President Obama’s contention that radical Islam was all but defeated.

His opponents say his antagonism towards Islamic terrorists became so intense that he failed to draw any distinction between the religion and its militant adherents. He also insisted the West was essentially at war with Islam.

There’s no sign he toned down the rhetoric after he stepped down from the DIA. In July last year, he tweeted: ‘In [the] next 24 hours, I dare Arab & Persian world “leaders” to step up to the plate and declare their Islamic ideology sick and must [be] healed.’

In another tweet, he intoned: ‘Fear of Muslims is RATIONAL’ and called on Arab leaders to admit their religion is ‘sick’.

His social media outbursts about Mrs Clinton proved equally incendiary. He and his son, Michael G. Flynn, used Twitter to spread ‘fake news’ conspiracy theories about the Clinton family. Last summer, he directed his internet followers to a tweet that falsely claimed Clinton was ‘wearing hijab in solidarity with Islamic terrorists’.

Six days before the presidential election, he posted a fake news story on Twitter that claimed that police and prosecutors in New York had found evidence linking Mrs Clinton and much of her senior campaign staff to paedophilia, money laundering, perjury and other crimes.

F lynn told his Twitter followers: ‘U decide.’ He was also found to have used social media to interact with members of the so-called ‘alt-Right’ movement — an alliance of ultra-conservatives who have been accused of being virulent white supremacists.

On top of all this, Mr Flynn was censured last year when he retweeted an anti-Semitic message, although he insisted the retweet was an accident and soon deleted the post.

Given such extraordinary behaviour over the years, it is perhaps surprising that this accident waiting to happen lasted as many as 24 days in Trump’s team.