DEFCON 5: Complete peace, no threats or conflicts.
DEFCON 4: This refers to normal, increased intelligence and the heightening of national security measures.
DEFCON 3: This refers to an increase to force readiness above normal.
DEFCON 2: This refers to a further increase in force readiness just below maximum readiness.
DEFCON 1: Total war. This refers to maximum readiness. It is not certain whether this has ever been used, but it is reserved for imminent or ongoing attack on US military forces or US territory by a foreign military power.