to the weapon's development, while still looking for ways in which its testing or deployment or use could be questioned. As he later recalled: Oppenheimer, Conant, and Lee DuBridge, another member who had opposed the H-bomb decision, left the GAC when their terms expired in August 1952. Truman had declined to reappoint them, as he wanted new voices on the committee who were more in support of H-bomb development. In addition, various opponents of Oppenheimer had communicated to Truman their desire that Oppenheimer leave the committee. Panels and study groups Oppenheimer played a role on a number of government panels and study projects during the late 1940s and early 1950s, some of which found him in the middle of controversies and power struggles. In 1948 Oppenheimer chaired the Department of Defense's Long-Range Objectives Panel, which looked at the military utility of nuclear weapons including how they might be delivered. After a year's worth of study, in spring 1952 Oppenheimer wrote the draft report of Project GABRIEL, which examined the dangers of nuclear fallout. Oppenheimer was also a member of the Science Advisory Committee of the Office of Defense Mobilization. Oppenheimer participated in Project Charles during 1951, which examined the possibility of creating an effective air defense of the United States against atomic attack, and in the follow-on Project East River in 1952, which, with Oppenheimer's input, recommended building a warning system that would provide one-hour notice to atomic attacks against American cities. Those two projects led to Project Lincoln in 1952, a large effort where Oppenheimer was one of the senior scientists. Undertaken at the MIT Lincoln Laboratory, which had recently been founded to study issues of air defense, this in turn led to the Lincoln Summer Study Group, where Oppenheimer became a key figure. Oppenheimer's and other scientists' urging that resources be allocated to air defense in preference to large retaliatory strike capabilities brought an immediate response of objection from the United States Air Force (USAF), and debate ensued about whether Oppenheimer and allied scientists, or the Air Force, was embracing an inflexible "Maginot Line" philosophy. In any case, the Summer Study Group's work eventually led to the building of the Distant Early Warning Line. Teller, who had been so uninterested in work on the atomic bomb at Los Alamos during the war that Oppenheimer had given him time instead to work on his own project of the hydrogen