focus on disarmament rather than inspections. In January 1960, as part of arms control planning and negotiation, he suggested the "threshold concept". Under this proposal, all nuclear tests above the level of seismic detection technology would be forbidden. After such an agreement, the US and USSR would work jointly to improve detection technology, revising the permissible test yield downward as techniques improved. This example of the "national means of technical verification", a euphemism for sensitive intelligence collection used in arms control, would provide safeguards, without raising the on-site inspection requirement to a level unacceptable to the Soviets. The US introduced the threshold concept to the Soviets at the Geneva arms control conference in January 1960 and the Soviets, in March, responded favorably, suggesting a threshold of a given seismic magnitude. Talks broke down as a result of the U-2 Crisis of 1960 in May. At the same time as the early nuclear arms control work, the Chairman of the Joint Chiefs of Staff, General Nathan F. Twining, sent a memorandum, in August 1959, to the Secretary of Defense, Neil McElroy, which suggested that the Strategic Air Command (SAC) formally be assigned responsibility to prepare the national nuclear target list, and a single plan for nuclear operations. Up to that point, the Army, Navy, and Air Force had done their own target planning. This had led to the same objectives being targeted multiple times by the different services. The separate service plans were not mutually supporting as in, for example, the Navy destroying an air defense facility on the route of an Air Force bomber going to a deeper target. While Twining had sent the memo to McElroy, the members of the Joint Chiefs of Staff disagreed on the policy during early 1960. Thomas Gates, who succeeded McElroy, asked President Dwight D. Eisenhower to decide the policy. Eisenhower said he would not "leave his successor with the monstrosity" of the uncoordinated and un-integrated forces that then existed. In early November 1960, he sent Kistiakowsky to SAC Headquarters in Omaha to evaluate its war plans. Initially, Kistiakowsky was not given access, and Eisenhower sent him back, with a much stronger set of orders for SAC officers to cooperate. Kistiakowsky's report, presented on November 29, described uncoordinated plans with huge numbers of targets, many of which would be attacked by multiple forces, resulting in overkill. Eisenhower was shocked by the plans, and focused