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Good morning.

Here’s what you need to know:

How Russian trolls worked

• The Justice Department indictment against 13 people and three companies lays out in riveting detail how Russia carried out a social media campaign to disrupt the 2016 presidential election.

Posing as activists, Russians organized rallies in American cities and played on political divisions with online posts that reached hundreds of thousands of people. Our correspondent in Moscow spoke to two former trolls about their efforts.

• Although Russia sought to manipulate the American electorate, political polarization was already well established in the U.S., our Interpreter columnists write.