One of the prosecution's initial difficulties was in deciding who should be tried. Many Nazis who might have been tried for war crimes fled after the war. Some were helped by the director of the German Church in Rome. Argentina proved to be one of the most popular havens for war criminals, many of whom were aided by ODESSA, an organization of SS men set up to help them. As many as ten thousand Nazis may have entered the United States. Some of them were helped by intelligence agencies interested in soliciting their help in the new cold war against communism. Operation Paper Clip was a deliberate program by the U.S. military that brought approximately sixteen hundred German scientists to America to work on various projects. For example, Arthur Rudolph became the director of the Saturn V moon rocket program. During the war...