RACHEL MARTIN, HOST:

The internment camps where Japanese-Americans were sent during World War II are a well-documented part of American history. One lesser-known camp was called Crystal City in southern Texas. And there, thousands of Japanese immigrants were detained along with many people of German and Italian descent. Hundreds of these Americans were then sent back to their countries of origin in exchange for Americans who were caught behind enemy lines when the war broke out.

Jan Jarboe Russell writes about these secret trade arrangements in a new book called "The Train To Crystal City: FDR's Secret Prisoner Exchange Program And America's Only Family Interment Camp During World War II." Russell writes about the families who came to Crystal City to be with their loved ones who have been detained.

JAN JARBOE RUSSELL: You had wives and fathers and children living in tiny huts in this 290-acre internment camp. It had schools. It had a swimming pool. Of course, it was an internment camp. It had barbed wire fences. It was under constant armed guard. All of the mail in and out of the camp was censored. But most heartbreaking is that President Roosevelt set up a division within the Department of State called the Special War Problems Division.

MARTIN: And this is where we get to the subtitle of your book "The Secret Prisoner Exchange Program."

RUSSELL: In the run-up to the war, the president realized that Americans would be tracked behind enemy lines in Germany and in Japan, especially. And he charged the Special War Problems Division with creating pools of people that he could trade for important Americans - soldiers, diplomats, businessmen, journalists, missionaries.

MARTIN: As you say, these were all Americans who happened to be living abroad when World War II breaks out. And the Roosevelt administration is trying to figure a way to get them home. And they think they have leverage by repatriating German-Americans, Italian-Americans, Japanese-Americans. Many of these people were born in America.

RUSSELL: Well, that was the tragedy of Crystal city, not the way the internees were treated. In about the 50 children of the camp that I spent time with and interviewed, some of them say that as hard as it was, those were the best years of their life because they were with their parents and their siblings. And so they aren't resentful about the Crystal City camp or their treatment. What they are resentful about it is that thousands of internees in Crystal City, including their American-born children, were exchanged into war for more important Americans.

MARTIN: You trace the story in the book of two young girls - Ingrid Eiserloh and Sumi Utsushigawa. What happened to those girls? What happened to their families when they were sent back to Germany and Japan?

RUSSELL: They went with their family. They all went together. The, you know - Sumi's father, who was a photographer in Los Angeles, and her mother went to Japan. And Ingrid and her brothers and sisters and her parents went to Germany. And they saw, of course, devastated lands, and they encountered unimaginable trouble while they were in Germany and Japan. The Germans thought that these American-born kids were spies. And despite all of that, these people - Ingrid and Sumi and a lot of other kids that were in the Crystal City camp traded with their families into war became astonishingly resilience American loyalists and made their way back to the United States after the war was over, even though their country had betrayed them.

MARTIN: In the end, you write about how Ingrid discovers that it wasn't just Americans who were exchanged for other Americans. She was sent back to Germany in exchange for the freedom of some European Jews.

RUSSELL: None of these people ever knew really who was getting out of the war. And I learned from a document at the National Holocaust Museum that a handful of Jews - 136 Jews in the Bergen-Belsen concentration camp were on the train coming out of Germany. And one of them is named Irene Hasenberg, who is roughly the same age as Ingrid. And I tell the story about when I was able to tell Ingrid this is who was on that train coming out. She said everything that happened to my family now makes sense to me. At least Irene and her brother and her mother got out.

MARTIN: The book is called "The Train To Crystal City." It is written by Jan Jarboe Russell. Thanks so much for talking with us, Jan.

RUSSELL: Thank you, Rachel. Transcript provided by NPR, Copyright NPR.