There are two responsibilities the president has with regard to nuclear weapons. The first is to direct the overall thrust of foreign policy both in the long term and in day to day matters. The nature of the policies he or she pursues, the skill with which s/he does so and the responses of other players in the arena determine level of readiness the nuclear components of the military maintain at any given moment in time. These levels are known as defense conditions, or DefCons in Pentagon speak. The lower the number the higher the state of readiness. Think of the DefCon levels as a group of serially connected safety locks on a gun. In DefCon 5 (no potentially nuclear conflict on the horizon) all the locks are engaged. Each step up the readiness ladder disengages another safety lock, until you get to DefCon 1, which means that nuclear combat is imminent and launch codes could be received from higher up any minute.