The Russians involved in the campaign executed it with almost perfect pitch — learning to mimic the way Americans talk online about politics so well that real Americans with whom they interacted found them in no way suspicious.

Such deception did not happen by accident. Russian trolls worked hard to sound like Americans and camouflage their political messages in other content.

“The first order of business was not to be unmasked,” said Lyudmila Savchuk, 36, a former employee of the Internet Research Agency who, like Mindiyarov, was not among those named in the indictment. “Their top specialty was to slip political ideas inside a wrapping that was as human as possible.”