DEFCON

DEFCON was a security rating utilized by the United States Armed Forces mentioned in Fallout 3, Fallout: New Vegas, Fallout 4 and Fallout 76.

Pre-War
DEFCON rates the current security status of the nation based on all available information. If threats occur, the DEFCON rating increases, ranging from 5 (low threat) to 1 (imminent nuclear war). Protocol outlined in Hopeville silo network security codes and Fort Constantine launch codes included USAF DEFCON clearance information.

In January 2077, following the United States' victory in the Battle of Anchorage, the rating was moved to DEFCON3. Later that month, the P.A.M. Initiative succeeded with the activation of an assaultron with a primary function of running statistical threat scenarios. P.A.M. reported that DEFCON was currently at 3 and that the odds of the alert state increasing that month was 12%. It stated that in order to increase global stability, a diverse set of detailed strategies must be adopted.

On October 23, 2077, at 9:13 AM, IONDS reported four probable launches and increased the nation's security level to DEFCON2. Four minutes later, NORAD confirmed the launch of nuclear weapons and DEFCON was raised to 1. Confirmed nuclear detonations were reported in Pennsylvania and New York before the network mainframe went offline. The DEFCON database archive at the Switchboard was subsequently corrupted and rendered inaccessible.

Post-War
In order to utilize the Appalachian Automated Launch System, Enclave President Thomas Eckhart intentionally released threats into the region in order to increase the DEFCON rating and in turn, grant access to keycards and the nuclear arsenal. The ability to shut down and repair the reactor that powers Sites Alpha, Bravo, and Charlie was dependent on the current DEFCON status.

These actions caused the rating in the region to remain at its highest level. Due to the rating remaining at DEFCON1, the Appalachian Automated Launch System continues to deliver nuclear keycards via automated convoys of cargobots. A DEFCON rating sign is located in the Whitespring Bunker's Command Center.

Appearances
DEFCON is mentioned in Fallout 3, Fallout: New Vegas, Fallout 4 and Fallout 76.

Behind the scenes
The real world acronym stands for Defense Readiness Condition.