What is DEFCON?


The defence readiness condition (DEFCON) is an alert state used by the United States Armed Forces.

The DEFCON system was developed by the Joint Chiefs of Staff (JCS) and unified and specified combatant commands. It prescribes five graduated levels of readiness (or states of alert) for the US military. It increases in severity from DEFCON 5 (least severe) to DEFCON 1 (most severe) to match varying military situations, with DEFCON 1 signalling the outbreak of nuclear warfare.

DEFCONs are a subsystem of a series of Alert Conditions, or LERTCONs, which also include Emergency Conditions (EMERGCONs).

Refer to National Command Authority (NCA).

Other Systems

Should not be confused with similar systems used by the US military, such as:


The DEFCON level is controlled primarily by the US president and the US Secretary of Defence through the Chairman of the JCS and the Combatant Commanders; each level defines specific security, activation and response scenarios for the personnel in question.

Different branches of the US Armed Forces (US Army, US Navy, US Air Force, US Marine Corps, US Coast Guard, and US Space Force) and different bases or command groups can be activated at different defence conditions. In general, there is no single DEFCON status for the world or country and it may be set to only include specific geographical areas. According to Air & Space/Smithsonian, as of 2014, the worldwide DEFCON level has never been more severe than DEFCON 3. The DEFCON 2 levels in the 1962 Cuban Missile Crisis and 1991 Gulf War were not worldwide.


Defence readiness conditions vary between many commands and have changed over time, and the United States Department of Defence uses exercise terms when referring to the DEFCON levels during exercises. This is to preclude the possibility of confusing exercise commands with actual operational commands. On 12 January 1966, NORAD “proposed the adoption of the readiness conditions of the JCS system”, and information about the levels was declassified in 2006:

Readiness ConditionExercise TermDescriptionReadiness
DEFCON 1COCKED PISTOLNuclear war is imminent or has already begun.Maximum readiness. Immediate response.
DEFCON 2FAST PACENext step to nuclear war.Armed forces ready to deploy and engage in less than six hours.
DEFCON 3ROUND HOUSEIncrease in force readiness above that required for normal readiness.Air Force ready to mobilise in 15 minutes.
DEFCON 4DOUBLE TAKEIncreased intelligence watch and strengthened security measures.Above normal readiness.
DEFCON 5FADE OUTLowest state of readiness.Normal readiness.

Brief History

After the North American Aerospace Defence Command (NORAD) was created, the command used different readiness levels (Normal, Increased, Maximum) subdivided into eight conditions, e.g. the “Maximum Readiness” level had two conditions “Air Defence Readiness” and “Air Defence 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 02 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 DEFCON 3) and Charlie/Delta under DEFCON 4, plus an “Emergency” level higher than DEFCON 1 with two conditions: “Defence Emergency” and the highest, “Air Defence Emergency” (“Hot Box” and “Big Noise” for exercises).

Instances of DEFCON 2 or 3


Cuban Missile Crisis

During the Cuban Missile Crisis on 16 to 28 October 1962, the US Armed Forces (with the exception of United States Army Europe (USAREUR)) were ordered to DEFCON 3. On 24 October, Strategic Air Command (SAC) was ordered to DEFCON 2, while the rest of the US Armed Forces remained at DEFCON 3. SAC remained at DEFCON 2 until 15 November.

Persian Gulf War

On 15 January 1991, the Joint Chiefs of Staff declared DEFCON 2 in the opening phase of Operation Desert Storm during the Persian Gulf War.


Yom Kippur War

On 06 October 1973, Egypt and Syria launched a joint attack on Israel resulting in the Yom Kippur War. The United States became concerned that the Soviet Union might intervene, and on 25 October, US forces, including Strategic Air Command, Continental Air Defence Command, European Command and the Sixth Fleet, were placed at DEFCON 3.

According to documents declassified in 2016, the move to DEFCON 3 was motivated by CIA reports indicating that the Soviet Union had sent a ship to Egypt carrying nuclear weapons along with two other amphibious vessels. Soviet troops never landed, although the ship supposedly transporting nuclear weapons did arrive in Egypt. Further details are unavailable and remain classified.

Over the following days, the various forces reverted to normal status with the Sixth Fleet standing down on 17 November.

Operation Paul Bunyan

Refer to Operation Paul Bunyan (1976).

Following the axe murder incident at Panmunjom on 18 August 1976, readiness levels for US forces in South Korea were increased to DEFCON 3, where they remained throughout Operation Paul Bunyan.

September 11 Attacks

During the September 11 attacks, Secretary of Defence Donald Rumsfeld ordered the DEFCON level be increased to 3, and also a stand-by for a possible increase to DEFCON 2. It was lowered to DEFCON 4 on 14 September.


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