DEFCON is a five-level military readiness system developed by JCS. System ranges from DEFCON 5 (least severe) to DEFCON 1 (most severe). DEFCON 1 signals impending nuclear warfare. System is controlled by president and Secretary of Defense
DEFCON measures US military alertness from 5 (peacetime) to 1 (nuclear war). Higher values indicate lower readiness, lower values indicate higher readiness. Different military branches can have different DEFCON levels