A defense readiness condition (DEFCON) is an alert posture used by the United States Armed Forces. The DEFCON system was developed by the Joint Chiefs of Staff and unified and specified combatant commands. It prescribes five graduated levels of readiness (or states of alert) for the U.S. military, and increase in severity from DEFCON 5 (least severe) to DEFCON 1 (most severe) to match varying military situations.
DEFCONs are a subsystem of a series of Alert Conditions, or LERTCONs, that also includes Emergency Conditions (EMERGCONs). There is no single DEFCON status for the country, and in fact different branches of the military can be at different levels of DEFCON at the same time. DEFCONs should not be confused with similar systems used by the U.S. military, such as Force Protection Conditions (FPCONS), Readiness Conditions (REDCONS), Information Operations Condition (INFOCON) and its future replacement Cyber Operations Condition (CYBERCON), and Watch Conditions (WATCHCONS), or the former Homeland Security Advisory System used by the United States Department of Homeland Security.
DEFCONs vary between many commands and have changed over time, and the United States Department of Defense uses exercise terms when referring to the DEFCONs. This is to preclude the possibility of confusing exercise commands with actual operational commands. "On 12 January 1960, NORAD "proposed the adoption of the readiness conditions of the JCS system", and information about the levels was declassified in 2006:
|Readiness condition||Exercise term||Description||Readiness||Color|
|DEFCON 1||COCKED PISTOL||Nuclear war is imminent||Maximum readiness||White|
|DEFCON 2||FAST PACE||Next step to nuclear war||Armed Forces ready to deploy and engage in less than 6 hours||Red|
|DEFCON 3||ROUND HOUSE||Increase in force readiness above that required for normal readiness||Air Force ready to mobilize in 15 minutes||Yellow|
|DEFCON 4||DOUBLE TAKE||Increased intelligence watch and strengthened security measures||Above normal readiness||Green|
|DEFCON 5||FADE OUT||Lowest state of readiness||Normal readiness||Blue|
Movies and popular culture often misuse the DEFCON system by "going to DEFCON 5" during a state of emergency. In fact, DEFCON 5 is the lowest state of readiness. The highest state, DEFCON 1, has never been called for.
After NORAD was created, the command used different readiness levels (Normal, Increased, Maximum) subdivided into 8 conditions, e.g., the "Maximum Readiness" level had two conditions "Air Defense Readiness" and "Air Defense Emergency". In October 1959, the JCS Chairman informed NORAD "that Canada and the U. S. had signed an agreement on increasing the operational readiness of NORAD forces during periods of international tension." After the agreement became effective on 2 October 1959, the JCS defined a system with DEFCONs in November 1959 for the military commands. The initial DEFCON system had "Alpha" and "Bravo" conditions (under DEFCON3) and Charlie/Delta under DEFCON4, plus an "Emergency" level higher than DEFCON1 with 2 conditions: "Defense Emergency" and the highest, "Air Defense Emergency" ("Hot Box" and "Big Noise" for exercises).
DEFCON 2 
Cuban Missile Crisis 
The highest confirmed DEFCON ever was Level 2. During the Cuban Missile Crisis on October 22, 1962, the U.S. Armed Forces were ordered to DEFCON 3. On October 26, Strategic Air Command (SAC) was ordered to DEFCON 2, while the rest of the U.S. Armed Forces remained at DEFCON 3. SAC remained at DEFCON 2 until November 15.
DEFCON 3 
Yom Kippur War 
September 11 attacks 
The third time the United States reached DEFCON 3 was during the September 11 attacks of 2001. U.S. Secretary of Defense Donald Rumsfeld ordered the increased DEFCON level and to stand by for an increase to DEFCON 2, which never came.
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, and each DEFCON level defines specific security, activation and response scenarios for the troops in question.
Popular culture 
- DEFCON was used in the films WarGames, Transformers, Thirteen Days, Independence Day, The Sum of All Fears, Crimson Tide, Armageddon, and Beavis and Butt-head Do America, and in the TV shows Stargate SG-1 and The West Wing, among many others.
- The real-time strategy game DEFCON simulates the outbreak of thermonuclear war, and advances through the DEFCON levels as each match progresses.
- Some IRC services such as Anope provide a DEFCON system defining several pre-set configurations to be enabled during an attempted attack on an IRC network.
- Hard dance organisation, Q-Dance hosts the yearly Defqon.1 Festival. The logo ironically is a peace sign.
The DEFCON Warning System 
The DEFCON Warning System, a privately run website/blog, is confused by some to represent the actual DEFCON Status of the United States. The site states that it is not associated with any government agency and does not report the DEFCON levels of any military branch.
In reality, there is no single DEFCON status for the country, as they are decided on an individual basis by respective branches of the military.
See also 
- Alert state
- Doomsday Clock
- HURCON — Hurricane Condition threat rating (military-developed scale).
- National Command Authority
- National Military Command Center
- UK Threat Levels — British equivalent to American DEFCON
- Joint Publication 1-02, Department of Defense Dictionary of Military and Associated Terms, 12 April 2001 (as amended through 19 August 2009)
- Sagan, Scott D. "Nuclear Alerts and Crisis Management" (Project Muse webpage). International Security. Volume 9 Number 4: 99–139.
- United States Army Corps of Engineers Savannah District (CESAS) Plan 500-1-12, 1 August 2001
- Chairman of the Joint Chiefs of Staff Instruction 6510.01F
- FOIA Release of "Emergency Action Procedures of the Joint Chiefs of Staff, Volume I - General" (April 24, 1981)
- NORAD/CONAD Historical Summary: July -December 1959 (Report). http://www.northcom.mil/FOIA/docs/1959%20NORAD%20CONAD%20History%20Jul-Dec.pdf. Retrieved 2013-05-04.
- Defcon Five at TV Tropes
- Sagan, S. D. (1985). Nuclear Alerts and Crisis Management. International Security, 9 (4), 99-139.
- DEFCON DEFense CONdition - United States Nuclear Forces
- 911 Commission Report