The dominant strategy of Russia's Facebook strategy: Sowing racial discord

At least 25% of the ads centered on issues involving crime and policing, often with a racial connotation. Separate ads, launched simultaneously, would stoke suspicion about how police treat black people in one ad, while another encouraged support for pro-police groups.

Divisive racial ad buys averaged about 44 per month from 2015 through the summer of 2016 before seeing a significant increase in the run-up to Election Day. Between September and November 2016, the number of race-related spots rose to 400. An additional 900 were posted after the November election through May 2017.

Only about 100 of the ads overtly mentioned support for Donald Trump or opposition to Hillary Clinton. A few dozen referenced questions about the U.S. election process and voting integrity, while a handful mentioned other candidates like Bernie Sanders, Ted Cruz or Jeb Bush.