The triggering event for the security hearing happened on November 7, 1953, when William Liscum Borden, who until earlier in the year had been the executive director of the United States Congress Joint Committee on Atomic Energy, sent Hoover a letter saying that "more probably than not J. Robert Oppenheimer is an agent of the Soviet Union." Eisenhower never exactly believed the allegations in the letter but felt compelled to move forward with an investigation, and on December 3, he ordered that a "blank wall" be placed between Oppenheimer and any government or military secrets.