Mueller charged 13 Russian nationals and 3 Russian entities for meddling in the election.

WASHINGTON, DC - JANUARY 20: Director of the Federal Bureau of Investigation Robert Mueller testifies at a Senate Judiciary Hearing focusing on the attempted bombing incident on Northwest Flight 253 January 20, 2009 in Washington, DC. The committee's goal is to improve the effectiveness of anti-terrorism tools and inter-agency communication in an attempt to increase airline safety after the attempted Christmas bombing of the flight. Ann Heisenfelt/Getty Images

In February, Mueller's office charged three Russian entities and 13 Russian nationals with "violating US criminal laws in order to interfere with US elections and political processes."

The charges were directed primarily at the Internet Research Agency (IRA), an infamous Russian "troll factory" located in St. Petersburg that focused on sowing political discord during the 2016 race by using Russian bots to spread fake news and pro-Trump propaganda on Facebook, Twitter, and other social-media platforms.

The 13 Russian nationals charged were indicted for working in "various capacities to carry out" the agency's "interference operations targeting the United States."

Among the defendants was Kremlin-allied Russian oligarch Yevgeniy Viktorovich Prigozhin, who is accused of using his companies, Concord Management and Consulting LLC and Concord Catering, to bankroll the IRA's work.

The charges did not allege that any American was a knowing participant in Russia's activities, or that the underlying conduct altered the outcome of the race.