The DEFCON (State of Defense) scale of the United States is a measure that is used to rate the alert level of the defense forces of the country. The DEFCON scale uses a minimum of 5, for normal peacetime status, and a maximum of 1, to indicate severe global situations, such as nuclear war. It is important to understand this system, both by culture and to avoid inappropriate use of the scale, such as saying "We are about to enter DEFCON six".
Steps
Part 1 of 3: DEFCON Reference Chart
DEFCON level | state level | Historical precedent |
---|---|---|
5 | Normal state in times of peace; | General "base" level during peacetime |
4 | Increased intelligence gathering and increased security measures | Sporadically during the Cold War, the War on Terror |
3 | Increase in the availability of the armed forces over normal levels; the Air Force ready to mobilize in 15 minutes | After the 9/11 attacks (2001), Yom Kippur War (1973), Operation Paul Bunyan (1976), after the Four Powers Talks (1960) |
2 | High availability; the armed forces are ready to deploy in six hours | Missile Crisis in Cuba (1962) |
1 | Maximum availability; all forces are ready for combat; imminent or probable nuclear war | None |
Part 2 of 3: Understand the levels of the DEFCON scale

Step 1. Learn to read the DEFCON scale
The DEFCON scale is a way of assigning a numerical value to the readiness of the American military. The highest DEFCON values are used to designate the levels that require the least availability, that is, during the most peaceful situations, while the lowest DEFCON levels are used to qualify the levels that require the highest availability of the armed forces., during the most tense situations, in which the possibility of a military action is higher. A DEFCON level 5 corresponds to normal times of peace, while a DEFCON level 1, which has never been reached, corresponds to the most dangerous situations, such as a thermonuclear war.
Consider that different DEFCON levels may be assigned to different military branches. For example, during the Cuban Missile Crisis, which is generally considered one of the most tense times in US military history, the Strategic Air Command remained in DEFCON 2, while the rest of the armed forces remained in DEFCON. 3

Step 2. Use DEFCON 5 to refer to times of peace
A DEFCON 5 level is very good, it is the condition used to designate military availability in normal times of peace. In DEFCON 5, the United States military does not take precautionary defense measures on a large scale, beyond those normally required.
Consider that DEFCON 5 is not necessarily a sign that the world is at peace; at this level there could be conflicts, some of them bigger, in other parts of the world. However, in this case the military judges that they do not pose a significant threat to national security

Step 3. Use DEFCON 4 to refer to elevated alertness
DEFCOM 4 is the first level of availability above the base value of DEFCOM 5 and is therefore a fairly slight increase in availability, although an upgrade from DEFCOM 5 to DEFCOM 4 is significant. This level means a greater intelligence gathering effort and, at times, increased national security measures. However, it is not common to indicate that the military, or the country, is in danger of imminent attack.
In the modern world, a DEFCOM 4 is sometimes thought to be issued after minor to moderate terrorist attacks, politically motivated assassinations, or when a possible conspiracy is discovered. Presumably, this is done in anticipation of further violence, in an attempt to prepare for and prevent it

Step 4. Use DEFCOM 3 to refer to military or politically tense situations
Situations that require a DEFCOM 3 are serious and, while they may not pose an immediate threat to the existence or stability of the United States, they require significant vigilance. At this level, the US military remains on a high level of alert, anticipating a mobilization; the Air Force in particular remains ready to begin operations only 15 minutes after receiving the notice. In addition, all military communications could be encrypted, according to classified protocols.
In the course of history, a DEFCOM was generally decreed 3 situations in which there were obvious possibilities of military action against the United States or its allies. For example, during Operation Paul Bunyan, which resulted in the issuance of a DEFCOM 3, two US officers were killed by North Korean forces in the Korean Demilitarized Zone (ZDC). In this case, a DEFCOM 3 was declared due to the possibility that any error in the resistance could spark open warfare along the Korean border, which was as politically and militarily tense an area as it is today

Step 5. Use DEFCOM 2 to refer to bigger threats
DEFCOM 2 establishes a greater increase in the availability of the armed forces, slightly less than the maximum availability. Combat forces are getting ready to begin major operations in just a few hours. An upgrade to DEFCOM 2 is very serious; These situations carry a significant risk of major military operations against the United States or its allies, including the use of nuclear weapons. Typically, DEFCOM 2 is reserved for anything other than the most militarily tense international situations.
The most notable moment a DEFCOM 2 was issued was during the Cuban Missile Crisis, although the upgrade was limited to Strategic Air Command. This is thought to be the only time a large-scale DEFCON 2 alert was issued, although since DEFCON-related information is generally classified, there is no certainty as to how many times this level of availability has been reached in the course. of history

Step 6. Use DEFCON 1 to refer to the high alert
DEFCON 1 indicates the maximum military availability; it is thought that with a DEFCON 1 level, the armed forces are ready for immediate action at all times. DEFCON 1 is reserved for the absolutely most dangerous and severe situations, including an impending or ongoing nuclear war involving the United States or one of its allies.
- Although as noted above, DEFCON levels are generally kept classified until after the fact, it is believed that a DEFCON 1 has never been declared for any branch of the United States military.
- Some limited and unverifiable evidence suggests that a DEFCON 1 may have been assigned to certain military units during the first Gulf War. However, if such claims are true, this assignment was only limited to individual units and not to entire branches of the military.
Part 3 of 3: Learn more about DEFCON

Step 1. Understand how DEFCON levels are assigned
The public does not fully understand the exact process the military uses to declare an increase in the level of the DEFCON scale. It is generally assumed that the Joint Chiefs of Staff, the highest-ranking commanders of the United States armed forces, decide to upgrade military readiness, with the approval of the president. However, some anecdotal evidence suggests that high-ranking military leaders may decide the level of the DEFCON scale without the consent of the president. For example, some sources report that the Strategic Air Command's decision to raise the DEFCON scale level to 2 during the Cuban Missile Crisis was made without the participation of President Kennedy.
Consider again that the precise actions of the armed forces at each DEFCON level are, for obvious reasons, secret. Therefore, most of the information that the general public has on this topic is based on old declassified documents or some references revealed after the fact. Although some non-military and non-governmental sources may claim that they know the current DEFCON level, there is no way to verify it

Step 2. Learn about other alert scales in the United States
The DEFCON scale is not the only measure that the government and the military use to rate their readiness against external and internal dangers. These include LERTCON, used by the United States and NATO allies, REDCON, used by individual United States military units, and so on. However, the most important alert scale, apart from DEFCON, is EMERGCON. These states of emergency, which have never been issued, are thought to be declared in the event of nuclear war and include both civilian and military directives. EMERGCON has the following two levels:
- Defense emergency, which is declared in the event of major hostile attacks against the United States or its allied forces abroad. Issued by an unidentified commander or higher authority.
- Air defense emergency, issued in the event of attacks against the United States, Canada, or military installations in Greenland. It is pronounced by the commander-in-chief of the North American Airspace Defense Command.
- Note that by definition all military forces remain at DEFCON 1 in the event an EMERGCON is issued.

Step 3. Research the history of the DEFCON scale
Although much of the history of the DEFCON scale is kept secret for obvious reasons, the declassified information that is available to the public is fascinating on its own. Conceived in the late 1950s, as a means of coordinating NORAD (North American Aerospace Defense Command) defense efforts between the United States and Canada, the DEFCON system has undergone several changes between the time of its creation and its current format.