We didn’t know it then, but August 2017 was the peak time for pro-Trump Russian Twitter trolls linked to the shadowy Internet Research Agency in St. Petersburg.

They were already busy before white supremacists gathered a year ago in Charlottesville, Virginia, for the Unite the Right rally. But after the event erupted into conflict, culminating in the death of counterprotester Heather Heyer on Aug. 12, the trolls fanned the flames, blaming the violence on the self-described "antifa" and Black Lives Matter.

Over the next week, Russia’s Twitter trolls continued with that line, backing Donald Trump through the storm that followed his condemnation of violence “on many sides,” and later rallying in support of Confederate statues.

Then, on Aug. 18, many of these trolls suddenly went silent. Twitter won’t confirm that it pulled the plug on them that day. But the handles that stopped tweeting on Aug. 18 were all on a list of banned accounts linked to the Internet Research Agency that the company provided to the House Intelligence Committee in November 2017.

These are the findings from a BuzzFeed News analysis of nearly 3 million tweets from Internet Research Agency accounts gathered by Darren Linvill and Patrick Warren of Clemson University in South Carolina. The researchers published their data with FiveThirtyEight because they want as many people as possible trying to understand how online trolls working for the Kremlin have helped foment division in the West.

In February, special counsel Robert Mueller indicted 13 Russian operatives employed by the Internet Research Agency for interfering in US politics with “a strategic goal to sow discord.” The indictment said the defendants operated social media accounts that, during the 2016 election campaign, backed Donald Trump and attacked Hillary Clinton.

The American public is bitterly divided with or without Russian trolls, and it’s unclear how much influence these accounts actually have on US politics. But they’re not going away anytime soon.

“America is under attack,” Linvill told BuzzFeed News. “I would assume that there’s a whole lot out there right now that Twitter doesn’t know about.”

Linvill and Warren categorized accounts identified by Twitter in the November 2017 list and a second one released in June this year into groups with distinctive identities. Most of those trying to influence US politics were “Left Trolls” and “Right Trolls.”

Many of the Left Trolls posed as supporters of Black Lives Matter, tweeting about hip-hop and other aspects of black culture as well as politics. They tended to support Bernie Sanders, disparage Hillary Clinton, and their activities spiked on Oct 6., 2016, when they blasted out more than 13,000 tweets — the day before WikiLeaks published emails from the Clinton campaign that had been hacked by Russian operatives.

By the summer of 2017, the Left Trolls were mostly a spent force. But that’s when more than 100 Right Trolls, which posed as Trump supporters, had their big surge, their output rising to more than 10,000 tweets a day until suddenly dropping away after Aug. 18 — presumably when Twitter banned many of the accounts.

