"How did the US goverment justify hiring former Nazi scientists, rather than trying them for war crimes?"

The U.S. government's hiring of former Nazi scientists, rather than trying them for war crimes, was justified through Operation Paperclip. Here are the steps explaining this:

1. End of World War II: As World War II was coming to an end, the Allies and the Soviet Union were scrambling to secure German technology and scientific expertise. The U.S. was particularly interested in the advancements the Germans had made in rocket technology.

2. Initiation of Operation Paperclip: In 1945, the U.S. initiated Operation Paperclip, a secret program to recruit and employ German scientists in the U.S. The name "Paperclip" came from the paperclips used to attach the scientists' new political profiles to their U.S. personnel files.

3. Justification: The U.S. justified this operation on the grounds of national security. The Cold War was beginning, and the U.S. was in a race with the Soviet Union to secure technological superiority. The U.S. government believed that by employing these scientists, they could both benefit from their knowledge and prevent them from aiding the Soviet Union.

4. Legal and Ethical Issues: The U.S. government was aware that many of these scientists were involved in war crimes. To circumvent this, they created false employment histories and expunged Nazi Party memberships and regime affiliations from the record. This allowed them to bypass President Truman's anti-Nazi order, which prohibited the hiring of Nazis by the U.S. government.

5. Impact: Many of these scientists, including Wernher von Braun, played key roles in the development of the U.S. space program and other military projects. However, the ethical implications of Operation Paperclip remain a subject of debate.