(CNN) US President Donald Trump's national security adviser Michael Flynn resigned from his post Monday night amid claims he misled the administration over his communications with Russia before Trump took office.

As Flynn stood down he admitted to giving "incomplete information" to Vice President Mike Pence regarding phone calls with Russia's ambassador to Washington. His resignation comes three days after Trump said he would look into the allegations.

Here's how it unfolded.

Trump appoints Flynn

Flynn was fired from his role as the director of Defense Intelligence Agency in 2014 by the Obama administration over claims he was a poor manager.

Sanctions and phone calls

December 29: The Obama administration announces of its diplomats over the country's alleged interference in the 2016 US election. Flynn and Russian ambassador Sergey Kislyak The Obama administration announces new sanctions against Russia and the expulsion of 35of its diplomats over the country's alleged interference in the 2016 US election. Flynn and Russian ambassador Sergey Kislyak speak several times on the phone the same day.

January 12: The Washington Post first reports that phone calls took place the day the White House announced Russian sanctions.

Pence refutes sanctions talk

JUST WATCHED Pence: Trump camp had no contact with Russia Replay More Videos ... MUST WATCH Pence: Trump camp had no contact with Russia 00:50

January 15: Trump's spokesman Sean Spicer confirms Flynn and Kislyak have been in communication, but Vice President-elect Mike Pence tells CBS that Trump's spokesman Sean Spicer confirms Flynn and Kislyak have been in communication, but Vice President-elect Mike Pence tells CBS that the two men did not talk sanctions.

"They did not discuss anything having to do with the United States' decision to expel diplomats or impose censure against Russia," Pence says.

And as questions swirl over the allegations, Trump officials then claim the communications were focused on scheduling a call between Trump and Russian President Vladimir Putin.

Flynn under investigation

Sally Yates delivered the message about Flynn to the White House.

January 23: Three days after Trump officially takes office, Three days after Trump officially takes office, US officials say investigators are scrutinizing several calls between Flynn and Russia's ambassador. Spicer, now the White House Press Secretary, reiterates that Flynn told him sanctions were not discussed in the calls.

At some point in January, the Justice Department warns the Trump administration that Flynn misled administration officials regarding his communications with Kislyak and is potentially vulnerable to blackmail by the Russians, according to a person familiar with the matter.

The message is delivered by Acting Attorney General Sally Yates, who is fired on January 30 for refusing to enforce Trump's controversial travel ban barring citizens from seven Muslim-majority countries from entering the US.

Official: Flynn did talk about sanctions

JUST WATCHED Spicer: Trump evaluating Flynn situation Replay More Videos ... MUST WATCH Spicer: Trump evaluating Flynn situation 01:28

February 13: Russia again denies the allegations that the men discussed sanctions, telling CNN: " Russia again denies the allegations that the men discussed sanctions, telling CNN: We have already said there haven't been any. " On the same day, reports surface of the Justice Department's warning to the administration regarding Flynn.

As the reports emerge, Trump's counselor Kellyanne Conway tells MSNBC that Flynn "does enjoy the full confidence of the president," but around an hour later, Spicer says Trump is "evaluating the situation."

Flynn resigns a few hours later , admitting he had "inadvertently briefed the Vice President-elect and others with incomplete information" regarding the phone calls with Kislyak and apologizes.