Representative Alexandria Ocasio-Cortez (D-NY) took to Twitter to state matter-of-factly that President Donald Trump’s administration is operating concentration camps for immigrants along the southern border of the United States.

AOC’s tweets started with a link to a June 13 Esquire article quoting Andrea Pitzer, the author of One Long Night: A Global History of Concentration Camps, on how detention centers run by the U.S. immigration system fit into a historical definition of concentration camps.

“We have what I would call a concentration camp system,” Pitzer told Esquire. “The definition of that in my book is ‘mass detention of civilians without trial.’” In an in-depth Twitter thread, posted on June 4, Pitzer broke down how the Trump administration’s immigration system fit the definition.

Ocasio-Cortez gave a boost to this assessment on June 18, tweeting, “This administration has established concentration camps on the southern border of the United States for immigrants, where they are being brutalized with dehumanizing conditions and dying. This is not hyperbole. It is the conclusion of expert analysis.”

Dealing with the all-too-common backlash she faces for taking a stand, the congresswoman from the Bronx continued her message.

“For the shrieking Republicans who don’t know the difference: Concentration camps are not the same as death camps,” AOC wrote. She referenced Pitzer’s definition of a concentration camp (civilians in detention en masse without trial), and said further, “That’s exactly what this administration is doing.”

Another expert also explained that to Esquire: Waitman Wade Beorn, a Holocaust and genocide studies historian told the magazine, "Things can be concentration camps without being Dachau or Auschwitz.”

“Concentration camps, in general, have always been designed — at the most basic level — to separate one group of people from another group,” Beorn said, “usually, because the majority group, or the creators of the camp, deem the people they're putting in it to be dangerous or undesirable in some way."

Trump has been clear on his view of migrants coming north from day one of his presidential campaign, in 2015, but some were critical of Ocasio-Cortez’s remarks.

Representative Liz Cheney (R-WY) chimed in to attack Ocasio-Cortez, accusing her of demeaning the memories of Holocaust victims and asking the former bartender to “do us all a favor and spend just a few minutes learning some actual history.”

“Hey, Rep. Cheney, since you’re so eager to ‘educate me,’ I’m curious: What do YOU call building mass camps of people being detained without a trial?” AOC responded to former vice president Dick Cheney’s daughter. “How would you dress up DHS’s mass separation of thousands [of] children at the border from their parents?”

AOC also explained the difference between concentration camps and death camps on Twitter, writing to investment advisor Ross Gerber, “This is an important distinction. One of the biggest lessons from that dark history is that it didn’t happen overnight. It emerged out of slow, increasingly concerning steps that acclimated the public to inhumane treatment.”

Ocasio-Cortez also retweeted Rabbi Danya Ruttenberg, who pointed out that in the example of the Holocaust, “Germany started with concentration camps in 1933. Death camps started in 1941.”

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