President Donald Trump announced via Twitter on Wednesday that he had “granted a Full Pardon” of his former national security advisor Michael T. Flynn, who had previously pled guilty twice to the crime of lying to the FBI.

The retired US army lieutenant general, the former head of the Defense Intelligence Agency, was the Trump administration’s first national security advisor for only 23 days. Flynn resigned on February 12, 2017 following revelations that he had concealed the nature of his December 2016 contacts with then-Russian Ambassador Sergey Kislyak.

President Trump tweeted on Wednesday afternoon, “It is my Great Honor to announce that General Michael T. Flynn has been granted a Full Pardon. Congratulations to @GenFlynn and his wonderful family, I know you will now have a truly fantastic Thanksgiving!”

The widely anticipated pardon likely brings to a conclusion the federal case against Flynn that included a series of unprecedented interventions by the White House over more than three years aimed at protecting the former Trump aide.

The pre-Thanksgiving presidential pardon—which relieves Flynn of any wrongdoing and restores all of his civil rights—may well be the beginning of a series of clemency acts by President Trump in the final weeks of his four-year term in the White House.

While he continues with a coup plot to overturn the results of the 2020 election—in which Democrat Joe Biden won the electoral and popular vote by substantial margins—and remain in the White House, Trump is moving to use the presidential power to pardon to protect his closest associates. Clearly, the Flynn pardon is in part an effort to head off potential civil and criminal charges against Trump himself and others in his family in the coming months and years.

The pardoning power of the US President is spelled out in the Article II, Section 2 of the Constitution, which states that the president “shall have Power to grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment.” So defined, this means the president cannot issue pardons for violations of state laws, for example, the numerous charges he and his children could face because of corrupt business operations in New York.

In the past, Trump has argued that he also has the power to pardon himself against any federal charges. For example, following the conclusion of the Mueller probe, he tweeted on June 4, 2018, “As has been stated by numerous legal scholars, I have the absolute right to PARDON myself, but why would I do that when I have done nothing wrong?”

It was Trump’s response to the investigation of Flynn—an attempt to pressure then-FBI director James Comey, to back off—that eventually resulted in the firing of Comey and the appointment of special counsel Robert Mueller to take over the investigation into alleged Russian efforts to influence the 2016 elections, which the FBI had begun in July 2016.

After tens of millions of dollars and nearly two years of investigation, the allegations emanating from the Democratic Party and the intelligence agencies that the Russian government of Vladimir Putin sought to influence the outcome of the 2016 elections in favor of the Trump campaign, and with its collaboration, were never substantiated.

Flynn, fired from his position as head of the Defense Intelligence Agency by Obama because of a clash over Mideast policy, was one of the most prominent early supporters of the Trump campaign. He spoke at the Republican National Convention and led chants in favor of imprisoning the Democratic presidential candidate, Hillary Clinton—an unprecedented action for a former top national security official.

There was nothing particularly novel about Flynn’s contacts with Kislyak during the transition period, when he spoke with many foreign officials in his capacity as Trump’s choice for national security advisor. Apparently under political pressure, however, he lied to Vice President Pence about the content of his discussions with the Russian ambassador, and when this was exposed by intelligence wiretaps of those conversations, Trump had to fire him.

On December 1, 2017, Flynn entered a plea bargain with Robert Mueller that included his agreement to cooperate with the investigation in exchange for pleading guilty to “willfully and knowingly” making “false, fictitious and fraudulent statements” to the FBI in relation to his conversations with the Russian ambassador.

In his statement of offense, Flynn said his, “false statements and omissions impeded and otherwise had a material impact on the FBI’s ongoing investigation into the existence of any links or coordination between individuals associated with the Campaign and Russia’s efforts to interfere with the 2016 presidential election.”

Sentencing was delayed multiple times as negotiations proceeded with Mueller over whether Flynn should serve any time at all for his offenses. A sentencing memo from Flynn’s attorneys on December 11, 2018 stated that he had been tricked into lying by FBI agents during questioning.

At the time, the New York Times reported that Flynn’s “decision to attack the FBI in his own plea for probation appeared to be a gambit for a pardon from Mr. Trump, whose former lawyer had broached the prospect last year with a lawyer for Mr. Flynn.”

One week later, Judge Emmet G. Sullivan rejected the claim that Flynn had been misled and stated, “I cannot assure that if you proceed today you will not receive a sentence of incarceration” and delayed sending the defendant to jail. During this hearing, Flynn restated his guilty plea and said that he was aware that lying to federal investigators was a crime at the time of his initial FBI interview in January 2017.

In August 2019, two months after Flynn fired his first legal team, the former Trump aide filed a motion to hold prosecutors in contempt for “malevolent conduct” and claiming that the federal government had attempted to smear him as a “Russian agent.” Judge Sullivan rejected these assertions and moved the sentencing date to January 2020.

After federal prosecutors submitted a memo calling for a sentence of up to six months, Flynn withdrew his guilty plea and, on January 29, issued a “personal declaration” that, under penalty of perjury, he was innocent and “did not consciously or intentionally lie” to the FBI about his conversations with Kislyak.

On month later, in an extraordinary development, Attorney General William Barr declared that there would be a review of Flynn’s case and on May 7 the Department of Justice filed a motion to dismiss all charges with prejudice. Judge Sullivan, however, refused to go along with this unprecedented legal whitewash, and the case was stalled for months as higher courts reviewed the issues.

With his term in office apparently likely to draw to a close before the legal wrangling reached a conclusion, Trump stepped in with the pardon, widely expected to be the first of a series for his closest cronies and supporters, including possibly his own family.