The defense readiness condition (DEFCON) is an alert state used by the United States Armed Forces.[1][2] For security reasons, the US military does not announce a DEFCON level to the public.[1]
The DEFCON system was developed by the Joint Chiefs of Staff (JCS) and unified and specified combatant commands.[3] It prescribes five graduated levels of readiness (or states of alert) for the U.S. military. It increases in severity from DEFCON 5 (least severe) to DEFCON 1 (most severe) to match varying military situations, with DEFCON 1 signaling the impending outbreak of nuclear warfare.[1][2]
DEFCONs are a subsystem of a series of "Alert Conditions", or LERTCONs, which also include Emergency Conditions (EMERGCONs).[4]
The DEFCON level is controlled primarily by the U.S. president and the U.S. Secretary of Defense through the Chairman of the Joint Chiefs of Staff and the Combatant Commanders; each level defines specific security, activation and response scenarios for the personnel in question.[1]
Different branches of the U.S. Armed Forces (i.e. U.S. Army, U.S. Navy, U.S. Air Force, U.S. Marine Corps, U.S. Coast Guard, U.S. Space Force) and different bases or command groups can be activated at different defense conditions. According to Air & Space/Smithsonian, as of 2022[update], the U.S. DEFCON level has never been more severe than DEFCON 3. The DEFCON 2 levels in the 1962 Cuban Missile Crisis and 1991 Gulf War applied only to the U.S. Strategic Air Command (SAC).[5][6]
DEFCONs should not be confused with similar systems used by the US military, such as Force Protection Conditions (FPCONS), Readiness Conditions (REDCONS), Information Operations Condition (INFOCON) and its future replacement Cyber Operations Condition (CYBERCON),[7] and Watch Conditions (WATCHCONS), or the former Homeland Security Advisory System used by the U.S. Department of Homeland Security.