Michael Flynn’s appointment as US national security adviser is a remarkable change in fortunes for a man all but written off two years ago when he was removed from his post as a Pentagon intelligence chief. The retired US Army three-star lieutenant-general was one of Donald Trump’s closest advisers and most ardent supporters during the campaign. Gen Flynn believes the US is losing a global war against Islamist extremism that may last for generations. Former US officials who worked closely with Gen Flynn described him as extremely smart, though a poor manager. Gen Flynn has been an almost evangelical believer in 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.” Gen 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, Gen Flynn has called the 2003 invasion of Iraq a strategic blunder. Even the areas where the two disagreed at first have been quickly smoothed over. 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.