From DEFCON 5 to DEFCON 1: understanding the DEFCON levels. (2023)

What is the DEFCON system?

DEFCON – that is, Defense Readiness Condition is a ranking system used by the United States military to signal their readiness for potential nuclear attacks or other national security threats.

DEFCON system was created by the U.S. Armed Forces in the 1950s, during the Cold War. The system was designed to provide a clear and concise way of communicating the current level of military readiness to military personnel and government officials.

The DEFCON system consists of five escalating levels of military readiness, with each level denoting a higher degree of preparedness. The DEFCON system’s lowest threat level is DEFCON 5, while DEFCON 1 represents the highest threat level: readiness for war.

Different levels of DEFCON:


This is the lowest state of readiness, which means that the United States is at peace, and there is no immediate threat to national security. This is the default state of readiness for the military.

United States Department of Defense has specific terminology to designate how its military exercises relate to DEFCON level situations.

The DEFCON 5 exercise term is ‘Fade Out’.


This level indicates an increased risk of a military conflict or terrorist attack. At DEFCON 4, the military is on heightened alert, and they may increase surveillance and intelligence-gathering activities. The military may also begin pre-positioning troops and equipment to be better prepared to respond to any potential threats.

The DEFCON 4 exercise term is ‘Double Take’.


DEFCON 3 indicates that there is a significant risk of an imminent attack. The military will further increase its surveillance and intelligence-gathering activities, and they may begin to prepare for a potential attack. This may involve deploying additional troops and equipment to key locations, such as air bases and naval ports.

The U.S. military has been at DEFCON 3 during times of heightened tension, including the Operation Paul Bunyan, the September 11 attacks and the Yom Kippur War.

It’s important to mention that DEFCON 3 does not indicate an actual state of war. Rather, it signifies heightened readiness whereby vacations are cancelled, troops are called back to their units and arrangements are made for deployment if required.

The DEFCON 3 exercise term is ‘Round House’.


This level represents an extremely high level of military readiness, with only a single step remaining until the highest level of readiness, DEFCON 1. At DEFCON 2, the military is prepared for an imminent attack, and they may take action to defend against the threat. This may involve deploying troops and equipment to defensive positions and increasing security measures at key installations.

The DEFCON level was raised to 2 during the Cuban Missile Crisis and Persian Gulf War, reflecting the high state of alert and readiness of the U.S. military at that time.

The DEFCON 2 exercise term is ‘Fast Pace’.


This is the highest level of readiness, which means that the United States is under imminent attack or is in the midst of a large-scale military conflict. At DEFCON 1, the military is fully mobilized and prepared for combat operations. This may involve the deployment of nuclear weapons, and the military will take all necessary steps to defend against the threat.

It has never publicly announced or confirmed that the United States has been at DEFCON 1. To the best of all available knowledge, then, it has never happened.

The DEFCON 1 exercise term is ‘Cocked Pistol’.

Readiness conditionExercise termDescriptionReadiness
DEFCON 1COCKED PISTOLNuclear war is inevitable or has already begunRequire maximum readiness and an immediate response
DEFCON 2FAST PACENext step to nuclear war has been takenThe armed forces are prepared to deploy and engage in combat in less than six hours
DEFCON 3ROUND HOUSEIncrease in force readiness above normal levelsAir Force is prepared to mobilize and be ready for action within a timeframe of 15 minutes
DEFCON 4DOUBLE TAKEIncrease in surveillance and security measures to enhance protection and vigilanceAbove normal readiness
DEFCON 5FADE OUTLowest state of readinessNormal readiness

It’s important to note that the DEFCON system is a flexible system that can be adjusted as needed to reflect the current threat environment. For example, the military may move from DEFCON 4 to DEFCON 3 in response to a specific threat, and then return to DEFCON 4 once the threat has passed.

Additionally, the specific actions that are taken at each DEFCON level may vary depending on the situation. For example, in response to the Cuban Missile Crisis that occurred from October 16 to 28, 1962, the U.S. Armed Forces were directed to DEFCON 3. Later, on October 24, Strategic Air Command received orders to raise their readiness level to DEFCON 2, while the other branches of the U.S. Armed Forces maintained DEFCON 3.

The military will assess the threat environment and take appropriate action to defend against the threat. Ultimately, the purpose of the DEFCON system is to ensure that the military is prepared to respond to any potential threat to national security.

Historical examples of when the DEFCON levels have been raised include:

The Gulf War in 1991: The DEFCON level was raised to 2 in response to Iraq’s invasion of Kuwait and the subsequent buildup of U.S. forces in the region.

The Cuban Missile Crisis in 1962: The political and military standoff between the United States and the Soviet Union during the height of the Cold War, over the installation of Soviet nuclear missiles in Cuba. The crisis lasted for 13 days, during which the world was thought to be on the brink of nuclear war. Eventually, the Soviet Union agreed to remove the missiles in exchange for a promise from the U.S. not to invade Cuba and to remove their missiles from Turkey.

As mentioned previously, the U.S. Armed Forces were initially directed to DEFCON 3. However, later, Strategic Air Command received orders to elevate their readiness level to DEFCON 2, while the other branches of the U.S. Armed Forces continued to maintain DEFCON 3.

The September 11 attacks in 2001: The United States raised the DEFCON level to 3 in response to the terrorist attacks on the World Trade Center and the Pentagon.

The Yom Kippur War in 1973: The conflict fought between Israel and a coalition of Arab states led by Egypt and Syria in October 1973. The U.S. supported Israel during the conflict, while the Soviet Union supported the Arab coalition. The war lasted for three weeks, and although Israel ultimately emerged victorious, both sides suffered heavy losses. DEFCON level was raised to 3 in response to this war.

Laws and regulations

While there are no specific laws or regulations that dictate the use of the DEFCON system, the President of the United States has the authority to change the DEFCON level as necessary in response to a threat. The DEFCON system is often used in conjunction with other emergency protocols, such as the Continuity of Government (COG) plan, which outlines procedures for maintaining the operations of the U.S. government during a national emergency.

In some cases, such as during the Cuban Missile Crisis, the public was made aware of the increase in the DEFCON level due to the seriousness of the situation. However, in other instances, such as during the Gulf War, the change in the DEFCON level was not widely publicized.

In general, the public may not be directly informed of changes in the DEFCON level unless there is a specific need for them to take action or to be informed of a potential threat. However, in the event of a significant national security threat, the government may choose to make an announcement to the public about the increase in the DEFCON level and what actions are being taken to respond to the threat.

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