Prior to the development of SIOP and survivable command and control, Eisenhower predelegated nuclear release authority to certain senior commanders. In April 1956, for example, he authorized Air Defense Command to use Genie air-to-air and Nike Hercules surface-to-air missiles during a surprise attack. There have continued to be Continuity of Nuclear Operations Plans (COOP), which designated enough subordinates who, in the event of the National Command Authority and immediate successors being killed in a "decapitation" attack, could still retaliate. While the details have never been made public, Eisenhower's predelegation, and a Federation of American Scientists summary, give a framework.