DEFCON 4 for heightened alertness. DEFCON 4 is the first level of readiness above the baseline value of DEFCON 5 and thus constitutes a fairly mild increase in readiness (though an increase from DEFCON 5 to DEFCON 4 is certainly significant).
DEFCON 4 for heightened alertness. DEFCON 4 is the first level of readiness above the baseline value of DEFCON 5 and thus constitutes a fairly mild increase in readiness (though an increase from DEFCON 5 to DEFCON 4 is certainly significant).