The chair of a pro-Trump super PAC, Carl Higbie, said there was precedent for Donald Trump's proposal of a Muslim registry: Japanese American internment during World War II.

Higbie told Fox News, "We did it during World War II with Japanese, which, you know, call it what you will."

But instead of saying that Japanese internment was a mistake — which, by virtually ever measure, it was because there was no justification for incarcerating more than 100,000 innocent people — Higbie added: "I'm not saying I agree with it, but in this case I absolutely believe the regional..." He was interrupted so he didn't finish that thought, but he hinted that there was some larger threat that made this idea somehow more acceptable.

And it's not just Trump allies that have had this ambiguous attitude toward Japanese internment. It's Trump himself. During the Republican primaries, Trump said he wasn't sure if he would've supported or opposed Japanese internment during World War II. He told Time Magazine that he "hates the concept of it," but added: "War is tough. And winning is tough. We don’t win anymore. We don’t win wars anymore."

To be clear, Japanese American internment is almost universally considered one of the most egregious things the United States has done to an entire ethnic group.

In case you need a refresher: From 1942 to 1945, the US forcibly relocated and incarcerated Japanese Americans in internment camps after Japan bombed Pearl Harbor.

It took a Supreme Court ruling to release the internees — a ruling that said it was illegal to detain citizens who are "concededly loyal" to the United States. But for many of the 110,000 Japanese Americans who were resettled, the damage was already done. They had little to go back to after being sequestered for two years.

The internment of Japanese Americans is a lesson in what can go wrong when a country reacts out of fear and categorically decides an entire ethnic group is dangerous, much like some US leaders are doing with Syrian refugees today.

But we're seeing more cases of politicians who try to normalize this policy. Earlier this year, Roanoke Mayor David Bowers had to apologize for suggesting that the way the US treated Japanese Americans during World War II was somehow okay.

I created the graphic at the top of this piece using data from the National Archives and Records Administration, which records every person interned in the early '40s. And as you wade through the data set, person by person, what you learn is that the people forced into internment camps weren't really foreigners at all; they were very much Americans. They weren't, as Roanoke's mayor initially put it, "Japanese foreign nationals." They were typically people ingrained into American culture — and the data shows it in more ways than one.

Nearly 70 percent were born in the US

About 90 percent of those interned had parents born in Japan. The data hints that those parents immigrated to the US in the first few decades of the 20th century — largely to the Pacific coast — and had children who were eventually forced into internment camps. Most of these internees were born between 1910 and 1930, meaning they were in their 20s and 30s when they entered these camps.

They were very much Americans

Most of the detained people could read, write, and speak English, which makes perfect sense since most of them went to school in America. In fact, 33,000 Japanese Americans enlisted to fight in World War II.

Oh, and internees organized baseball games at some of the camps.

But it gets even worse: Many of them had never even been to Japan

Almost half the internees had never even been to Japan. Only a fraction spent more than a decade there.

In December 1944, the Supreme Court said it was illegal to detain citizens who were "concededly loyal" to the United States, and in January 1945 the internees were released.

Only in 1988 did the US apologize and pay $20,000 in reparations to surviving detainees. And only eight years ago did the US Census Bureau finally admit to helping the government round up Japanese Americans after Pearl Harbor.

Much thanks to JapaneseRelocation.org, which shared a clean data set with me. If you want to see the record of a specific internee, this is a great resource.