but although it was more advanced than the American bombs of 1946, Britain was still several years behind in nuclear weapons technology. On 1 November, the United States conducted Ivy Mike, the first nuclear test of a true thermonuclear device (also known as a hydrogen bomb). The JCAE saw little benefit for the US from sharing technology with Britain. The Soviet Union responded to Ivy Mike with the test of Joe 4, a boosted fission weapon on 12 August 1953. That prompted President Dwight Eisenhower, who was inaugurated in January 1953, to inform the US Congress that the McMahon Act, which he considered a "terrible piece of legislation" and "one of the most deplorable incidents in American history of which he personally felt ashamed", was obsolete.