DEFCON DEFense CONdition - United States Nuclear Forces

I always wondered what this stuff meant.
DEFCON DEFense CONdition - United States Nuclear Forces: "DEFCON 5 Normal peacetime readiness
DEFCON 4 Normal, increased intelligence and strengthened security measures
DEFCON 3 Increase in force readiness above normal readiness
DEFCON 2 Further Increase in force readiness, but less than maximum readiness
DEFCON 1 Maximum force readiness."