William Cummings

USA TODAY

President Trump's national security adviser didn't last a month on the job.

Retired Army lieutenant general Michael Flynn helped shape Trump's views on combatting terrorism and the president appointed him to one of the most influential positions in his administration. But questions about Flynn's ties to Russia eventually led to his resignation.

Here are the key elements to Flynn's rise and fall:

A leader in military intelligence

Flynn, who was highly regarded by many in the military and intelligence communities, developed a reputation as being an innovative thinker who sometimes fought against an entrenched military bureaucracy. He was the top intelligence official in Iraq and Afghanistan during the height of the American involvement in the wars there. He is credited with helping develop a system to effectively use battlefield intelligence to hunt down terrorists and destroy their networks.

Hired and fired as director of the DIA

In 2012, then-president Barack Obama appointed Flynn director of the Defense Intelligence Agency, the Pentagon’s top intelligence official. He was dismissed from the job in 2014 for his combative style, including reported clashes with former director of national intelligence James Clapper.

A fierce Obama critic

Flynn became an outspoken critic of Obama and his administration's anti-terrorism efforts. Flynn said the U.S. is at war with "radical Islamic terrorism" and was highly critical of the president's refusal to use the term. Obama said he did not wish to frame the war on terror along religious lines. His critical view of Obama's approach to national security and his hardline stance on terrorism meshed with Trump's views, leading him to become a trusted Trump adviser on national security issues.

Controversial statements about Islam

While Flynn's position on Islamic extremism endeared him to Trump and many of his supporters, it also made him highly controversial. In February 2016 he tweeted that "fear of Muslims is rational." He said Islam is not a religion, but a political ideology and compared it to a cancer, according to the Dallas Morning News. He also has falsely claimed that Shariah law is spreading in the U.S.

Ties to Russia

The role of national security adviser is not an official Cabinet position and doesn't require Senate confirmation. If it did, Flynn would have had a tough confirmation fight on his hands for his appearances on Russia Today — the network identified by U.S. intelligence agencies as part of Russia's propaganda campaign against Democratic candidate Hillary Clinton. He also made a paid appearance alongside Russian leader Vladimir Putin at a lavish anniversary party in Moscow for the Kremlin-funded network in 2015. House Democrats argued this violated the emoluments clause, which prohibits any federal officer from receiving payment from a foreign country without approval by Congress.

Questionable chats with Russia's ambassador

Flynn's resignation followed allegations that he might have interfered with U.S. relations with Russia while a private citizen by discussing the sanctions the Obama White House imposed on Russia — in retaliation for alleged interference in the presidential election — with Ambassador Sergey Kislyak. Flynn denied discussing the sanctions with Kislyak but then changed his story, telling The Washington Post he "couldn't be certain that the topic never came up." Vice President Pence had publicly defended Flynn, believing the former general's denials that he did not discuss the sanctions. In his resignation letter, Flynn conceded that he "briefed the vice-president elect and others with incomplete information regarding my phone calls with the Russian Ambassador."

Read More:

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Contributing: Heidi Przybyla, Eliza Collins, Jim Michaels and Gregory Korte