The heavily redacted memo added that this included “first-hand” details about links between the Trump election team and Russian officials and lines of inquiry “concerning links or coordination between the Russian government and individuals associated with the Trump campaign”.

While Flynn initially faced up to five years in federal prison for lying to the FBI about his discussions with former Russian ambassador Sergey Kislyak, he may now serve no time at all.

“A sentence at the low end of the guideline range — including a sentence that does not impose a term of incarceration — is appropriate and warranted,” Mueller wrote in the memo, which highlighted Flynn’s “exemplary” military and public service as a contributing factor.

“(Flynn) deserves credit for accepting responsibility in a timely fashion and substantially assisting the government,” Mueller added.

It had been thought details of Russian collusion might be included in the memo, but due to “sensitive information about ongoing investigations”, certain aspects have been sealed. It does, however, provide a tantalizing glimpse of Flynn’s interactions with Russia and his communications with other members of the Trump campaign and transition team.

More importantly, it also points at future difficulties for President Trump. Most notably, where it mentions Flynn’s assistance in “a criminal investigation”. The precise nature — and subject — of these charges, however, are hidden behind a large section of redacted text.

Some experts have speculated that the memo is indicative of Mueller’s modus operandi and that his final report to the Justice Department may never be released, even in part. Instead, it’s believed that Mueller will provide substantial information about his investigation in court filings that detail recommendations for sentencing Trump associates who have pleaded guilty or were convicted of federal charges, including Michael Cohen, Rick Gates, Paul Manafort, and Flynn.

Like Flynn, who pleaded guilty to lying to the FBI December 2017, a number of other officials in the Trump administration initially claimed to have had no contact or limited contact with Russian officials and intermediaries, only to later be tripped up, admit, or file new disclosures.

This includes former Attorney General Jeff Sessions, whose failure to detail his meetings led to him recusing himself from any investigation related to potential Russian interference in the 2016 presidential investigation, and ultimately to Deputy Attorney General Rod Rosenstein appointing Mueller as special counsel.

President Trump demanded Flynn’s resignation on Feb. 13, 2017. His press secretary at the time said it was due to Flynn misleading Vice President Mike Pence and others. Trump later reportedly regretted firing Flynn, and discussed plans to bring him back into the administration.