Bush was one of seven directors (including W. Averell Harriman) of the Union Banking Corporation, an investment bank that operated as a clearing house for many assets and enterprises held by German steel magnate Fritz Thyssen. In July 1942, the bank was suspected of holding gold on behalf of Nazi leaders. A subsequent government investigation disproved those allegations but confirmed the Thyssens' control, and in October 1942 the United States seized the bank under the Trading with the Enemy Act and held the assets for the duration of World War II.
According to journalist Joe Conason, Prescott Bush's involvement with UBC was purely commercial and he was not a Nazi sympathizer. The Anti-Defamation League and historian Herbert Parmet agreed with that assessment.