Defensive Readiness Condition (DEFCON) is an alert posture used by the United States armed forces. It is mentioned many times in the Call of Duty: Black Ops campaign in the mission briefings as a sign of warning with Nova-6 before released.
Call of Duty: Black Ops
The first DEFCON level in Call of Duty: Black Ops's campaign is at DEFCON 4 but is changed quickly to L3 in "WMD". Before "Rebirth", DEFCON is moved to L2, which means preparations for war. Finally, DEFCON is moved down to its final level, L1, meaning war is imminent before a US team comprised of Mason, Hudson and Weaver stopped the Nova-6 threat.
DEFCON is seen in the Zombies map "Five", where players have to switch all of the DEFCON switches, with each switch to DEFCON level will lower by one. If the DEFCON level reaches five, the DEFCON or Pack-a-Punch room will open, containing a Pack-a-Punch machine. In order to gain access to the Pack-a-Punch room again, all DEFCON switches must be re-activated.
- In "Five", there is a pun on the word DEFCON, calling it death-con instead.