of 1949 there was no design that worked, and no certainty that a practical bomb could be built if there was one. He cautioned that the "Super" would probably require large amounts of tritium, which could only be acquired by diverting the AEC's nuclear reactors from plutonium production. Strauss found allies in Lawrence and Edward Teller, who had headed the "Super" group at Los Alamos during the war. When the matter was referred to the GAC, it unanimously voted against a crash program to develop the "Super". Without a workable design, it seemed foolish to divert resources from atomic bombs. Nor was there an obvious military need. Despite this, Truman authorized that H-bomb work proceed on January 31, 1950. Teller, Fermi, John von Neumann, and Stan Ulam struggled to find a working design, and in February 1951, Ulam and Teller finally devised one. After reviewing the design and data gathered by the Operation Greenhouse tests in May 1951, Oppenheimer acknowledged that the "New Super" was technically feasible. Teller left Los Alamos to help found, with Lawrence, a second weapons laboratory, the Lawrence Livermore National Laboratory, in 1952. Thermonuclear strategic weapons, prior to the development of long-range ballistic missiles, would necessarily be delivered by long-range bombers under the control of the relatively new United States Air Force. In projects and study groups such as Project Vista and the Lincoln Summer Study Group however, Oppenheimer pushed for smaller "tactical" nuclear weapons that would be more useful against enemy troops in a limited theater conflict and which would be under control of the Army. He also proposed investments in air defense against nuclear attack, which would potentially take resources away from the Air Force's retaliatory strike mission. As chair of the State Department Panel of Consultants on Disarmament, Oppenheimer argued for postponing the Ivy Mike first test of a hydrogen device. These stances led the Air Force to view Oppenheimer's positions and influence with bitterness and suspicion. Claims made in the Borden letter On November 7, 1953, J. Edgar Hoover was sent a letter concerning Oppenheimer by William Liscum Borden, former executive director of Congress' Joint Atomic Energy Committee. In the letter, Borden stated his opinion "based upon years of study, of the available classified evidence, that more probably than not J. Robert Oppenheimer is an agent of the Soviet Union." The letter was based upon the government's massive investigative dossier on Oppenheimer,