In 1950, the Atomic Energy Commission asked "Scientific American" not to publish an article by Bethe that it claimed revealed classified information about the hydrogen bomb. "Scientific American" reluctantly agreed to stop the presses and make changes in the article, and to recall and burn the 3,000 copies that had already been printed. The 1951 arrest of Klaus Fuchs, Harry Gold, David Greenglass, Morton Sobell and Julius and Ethel Rosenberg who, according to FBI Director J. Edgar Hoover, "stole the basic secrets of nuclear fission", caused great concern. President Dwight D. Eisenhower denied the Rosenbergs clemency on the grounds that their actions "could well result in the deaths of many, many thousands of innocent citizens", and they were executed. After the Soviet Union detonated Joe 4 in August 1953, newspapers proclaimed that the Soviets had tested a hydrogen bomb. In fact it was only a boosted fission device, but the veil of secrecy covering the thermonuclear program prevented scientists from informing the public.