A timeline of Flynn's White House tenure:

Nov. 18: President-elect Donald Trump offered Flynn the post of national security adviser, elevating the retired general who saw Islamist militancy as a global threat.

Dec. 29: Former President Barack Obama ejected dozens of suspected Russian intelligence operatives from the United States and imposed sanctions on Russia after U.S. intelligence officials concluded that the nation had ordered the hacking of the Democratic National Committee. In a phone conversation around the same time, Flynn discussed the sanctions with the Russian ambassador, Sergey Kislyak, and urged Russia not to retaliate because doing so could complicate future cooperation between the two nations. The call was captured on a routine wiretap of diplomats' calls.

Jan. 15: Vice President-elect Mike Pence was asked about the phone call on CBS following a report on Flynn's ties to Russia and his conversation with Kislyak. Pence denied that sanctions had been discussed.

Jan. 26: After FBI agents interviewed Flynn about the call, the acting attorney general, Sally Yates, told Donald McGahn, the new White House counsel, that Flynn was vulnerable to Russian blackmail due to the discrepancy between his statements and what intelligence officials knew about the call.

Feb. 10: Trump said he planned to "look into" Flynn's conversation with Kislyak. "I don't know about that," Trump told reporters on Air Force One. "I haven't seen it." The White House publicly denied that sanctions were discussed.

Feb. 13: Flynn resigned, writing, "I inadvertently briefed the vice president-elect and others with incomplete information regarding my phone calls with the Russian ambassador."

New York Times