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Boston city officials have announced a heavy police presence will be on hand to contain potential violence at competing protests scheduled Saturday in Boston Common, the city's most historic park.

What those officers — and protesters — will encounter is unclear. The event started with a permit for up to 100 people with the stated purpose of demonstrating for free speech, but counter-protests were planned when other local activist groups, including Black Lives Matter, noticed two of the scheduled speakers have ties to the alt-right, and one of those two attended the white nationalist rally in Charlottesville.

"We're expecting about 20,000 to 30,000," said one counter-protest organizer, Monica Cannon. "We plan to send a really strong message that ... you don't get to come here and do this."

A previous demonstration by Boston Free Speech, the group that applied for the original permit, was organized in a different park in Boston earlier this year. Also billed as a pro-Constitution event, many attendees were affiliated with alt-right and white supremacist groups, and speakers included one Augustus Invictus, who told his audience to prepare themselves to fight a second Civil War. Boston Free Speech abridged Saturday's schedule in response to the planned counter-protests. Several of the more controversial speakers, including Invictus, are no longer on the docket.