Former Trump National Security adviser Michael Flynn will plead guilty today to lying to the FBI. Here’s what we know and don’t know about the specific incidents surrounding Flynn’s false statements. Both statements involve Flynn’s discussions with Russian Ambassador Sergey Kislyak, conversations that have drawn legal scrutiny and even made some national security officials worry that Flynn was vulnerable to blackmail from Russia.

Dec. 22, 2016

The charging documents detail two false statements made by Flynn. The first occurred on or around December 22, 2016, according to the charging documents, and involved a claim that he “did not ask the Russian Ambassador to delay the vote on or defeat a pending United Nations Security Council resolution.” The charging docs, in other words, suggest Flynn did ask the Russian ambassador to delay the vote.

This is apparently a reference to a U.N. Security Council resolution condemning Israeli settlements that was passed on December 23, 2016. Russia opposed the resolution and Russian diplomats publicly said that they tried to delay the vote. At the time, Flynn was not yet serving as Trump’s National Security adviser. His tenure in the position lasted just 24 days — he resigned after he admitted that he misled Vice President Mike Pence and other administration officials about his conversations with the Russian ambassador.

Dec. 29, 2016

Flynn’s second false statement occurred on or around December 29, 2016. The documents suggest Flynn asked the Russian Ambassador “to refrain from escalating the situation in response to sanctions that the United States had imposed against Russia,” and then lied about it to the FBI. Flynn said he “did not recall the Russian Ambassador subsequently telling him that Russia had chosen to moderate its response to those sanctions as a result of his request.”

On December 29, the Obama administration imposed sanctions against two Russian intelligence services and expelled 35 Russian operatives from the U.S. in retaliation for alleged Russian meddling in the 2016 election. In a surprise move, Russian President Vladimir Putin announced that he would not retaliate by kicking U.S. diplomats out of Moscow.

“We will not create any problems for U.S. diplomats. We will not expel anyone,” Putin said. “It is regrettable that the Obama administration is ending its term in this manner.” Putin also said he would “plan further steps for restoring the Russian-American relationship based in the policies enacted by the administration of President Donald Trump.”

A day later, Trump tweeted: “Great move on delay (by V. Putin). “I always knew he was very smart!”

When Flynn made the false statements

Flynn reportedly made the false statements in a January 24 interview with the FBI. Flynn told the Washington Post that he denied discussing sanctions with the Russian ambassador, but later issued a statement saying “that while he had no recollection of discussing sanctions, he couldn’t be certain that the topic never came up.”

Previously, on January 14, Flynn met privately with Vice President-elect Mike Pence and told him that he had not discussed sanctions with Kislyak. Two days after Flynn’s interview with the FBI, Sally Yates, who was then the acting attorney general, warned the White House that Flynn’s call with the Russian ambassador had been monitored, offering proof that he was mischaracterizing the conversation.