Although he was born to German parents and raised in fascist Spain, Half Zantop was a beloved and respected member of the American scientific community, and succeeding in becoming fully a part of that community. Other foreign-born scientists have not been so lucky. During World War II, international connections and knowledge of the German language aroused nativist suspicions, even of scientists whose intellectual standing was of the highest levels. An example is Harald Sverdrup.

In the summer of 1941, Sverdrup, the Norwegian-born Director of the Scripps Institution of Oceanography (SIO) in La Jolla, California, was denied security clearance to work on Navy-sponsored research in underwater acoustics applied to anti-submarine warfare. The official story of Sverdrup’s clearance denial was the risk of blackmail over relatives in occupied Norway. Declassified documents tell a different story. Although Sverdrup’s integrity was defended on the highest levels of U.S. science, doubt was cast upon him by faculty at SIO, who accused him of being a Nazi sympathizer. The root of their suspicion was personal distrust, based in significant part on Sverdrup’s knowledge of the German language and his close connections to scientists in Germany. These doubts became grounds for withholding clearance, until Roger Revelle, a former student of Sverdrup working within the Navy, was able to obtain a limited clearance for Sverdrup to develop techniques for forecasting surf conditions during amphibious assaults. After the war, this work was credited with saving many lives, but at the time it placed Sverdrup out of the mainstream of Navy-sponsored oceanographic research. In being denied access to major areas of scientific work, Sverdrup’s position as a leader of American oceanography was undermined, as his vision of international oceanography in pursuit of natural knowledge gave way to the interpretation of oceanography as a matter of national security. Sverdrup's case is illustrative of the difficulties that foreign-born scientists have sometimes had in American science.