The atomic bombs dropped on Hiroshima and Nagasaki may have put an end to World War II, but they weren’t the only destructive weaponry developed during the war. From nerve and disease agents to the feared and coveted V-1 and V-2 rockets, Nazi scientists worked on an impressive arsenal. As the war came to a close in 1945, both American and Russian officials began scheming to get that technology for themselves. So it came to pass that 71 years ago today, 88 Nazi scientists arrived in the United States and were promptly put to work for Uncle Sam.

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In the days and weeks after Germany’s surrender, American troops combed the European countryside in search of hidden caches of weaponry to collect. They came across facets of the Nazi war machine that the top brass were shocked to see, writer Annie Jacobsen told NPR’s All Things Considered in 2014. Jacobson wrote about both the mission and the scientists in her book, Operation Paperclip: The Secret Intelligence Program That Brought Nazi Scientists To America.

“One example was they had no idea that Hitler had created this whole arsenal of nerve agents,” Jacobsen says. “They had no idea that Hitler was working on a bubonic plague weapon. That is really where Paperclip began, which was suddenly the Pentagon realizing, ‘Wait a minute, we need these weapons for ourselves.’"

But just studying the weapons wasn't enough, and the U.S. military wasn’t the only country eyeing Nazi scientists—their one-time allies in the Soviet Union were doing the same thing. If the Soviets were going to press their former enemies into service, American military officials didn't want to be left behind. So the U.S. government hatched a plan to bring 88 Nazi scientists captured during the fall of the Nazi Germany back to America and get them back on the job. Only this time, according to History.com, they were working for the U.S. under a project known as “Operation Paperclip.”

While the military did what they could to whitewash the pasts of their “prisoners of peace,” as some of the scientists called themselves, many had serious skeletons in their closets. For example, Wernher von Braun was not just one of the brains behind the V-2 rocket program, but had intimate knowledge of what was going on in the concentration camps. Von Braun himself hand-picked people from horrific places, including Buchenwald concentration camp, to work to the bone building his rockets, Jacobsen tells NPR.

Operation Paperclip was top secret at the time. After all, the devices these men helped design killed many people throughout Europe, not to mention the deaths their government was responsible for on the battlefield and in the concentration camps. Even agents with the Justice Department's Office of Special Investigations, which the U.S. government tasked with hunting down top Nazi officers who went on the lam after the war, were unaware for decades of the extent to which government officials were collaborating with their quarry, Toby Harnden reported for The Telegraph in 2010.

While many of the men who were brought to the U.S. under the program were undoubtedly instrumental in scientific advancements like the Apollo program, they were also supportive and responsible for some of the horrors experienced by victims of the Holocaust. Operation Paperclip has certainly left a questionable legacy.