What Is DEFCON? The 5 Levels Explained, With History

Short answer: DEFCON, short for “defense readiness condition,” is the U.S. military’s five-step scale of alert, running from DEFCON 5, the lowest state of readiness, to DEFCON 1, ready for war. The Joint Chiefs of Staff created the system in 1959. Only once have U.S. forces gone to DEFCON 2: the Strategic Air Command (SAC), on October 24, 1962, during the Cuban Missile Crisis. Since then, the United States has never gone above DEFCON 3, according to the National Security Archive at George Washington University.

Last updated: October 27, 2026

What is DEFCON?

DEFCON is the system the Joint Chiefs of Staff use to raise or lower the readiness of U.S. forces in steps. The National Security Archive has published the founding document, JCS Staff Memorandum 833-59, “Uniform Readiness Conditions”, dated August 25, 1959, and revised in January 1961.

According to the Archive, the Joint Chiefs set up the system “to provide military forces with a ‘uniform system of progressive readiness conditions.'” Each level has a code name. The memorandum lists them in an appendix, from “Fade Out” at the bottom to “Cocked Pistol” at the top.

DEFCON is a military readiness scale, not a public warning. It tells commands how far to prepare, and it can apply worldwide or to a single region.

The five DEFCON levels

Level	Code name	Meaning	Example in our sources
DEFCON 5	Fade Out	Lowest level of operational readiness	—
DEFCON 4	Double Take	Between DEFCON 5 and DEFCON 3	—
DEFCON 3	Round House	Higher readiness; in 1973 it meant readying nuclear-armed units	1962, 1973, 1976 (Korea), 1979 (Korea), 2001
DEFCON 2	Fast Pace	“A further increase in military force readiness which is less than maximum readiness”	SAC only, October 24, 1962
DEFCON 1	Cocked Pistol	Ready to go to war	Never ordered

The descriptions of DEFCON 5, DEFCON 1 and DEFCON 2 come from the National Security Archive’s summary of the 1959 memorandum and of JCS regulations. Lower numbers mean higher alert, which is why “DEFCON 1” is the most serious level.

DEFCON 2 and the Cuban Missile Crisis

The closest the United States has come to the top of the scale was in October 1962. The Archive’s briefing book Crises, Alerts, and DEFCONs, 1961-1976 says U.S. forces went to DEFCON 3 during the crisis and that, on October 24, “SAC went to DEFCON 2, the first and only time U.S. forces have gone to that alert level.”

The scale of that alert was enormous. Within a day, SAC had on alert “1,436 bombers, 145 ICBMs, and about 2,900 nuclear weapons.” Its airborne alert used one-eighth of the bomber fleet, with more than 2,000 launches and 65 B-52s kept in the air continuously.

The Archive concludes that the crisis “made tangible the grave danger of nuclear confrontations.” Those bombers and missiles are the forces described in our guide to the nuclear triad.

DEFCON 3 in 1973

The last worldwide DEFCON before 2001 came during the October 1973 Arab-Israeli war. The Archive says that at 11:41 p.m. on October 24, Joint Chiefs Chairman Adm. Thomas Moorer “ordered U.S. military commands to raise their alert levels to DEFCON 3.”

Moorer’s own memorandum, published by the State Department’s Office of the Historian in Foreign Relations of the United States, 1969–1976, Volume XXV, Document 269, lists the steps taken that night:

“Set DEFCON III”
Moved the carrier John F. Kennedy from west of Gibraltar into the Mediterranean
Alerted European forces and the 82d Airborne Division
Recalled 75 B-52s from Guam

The memo also records that the alert would lead to recalls of personnel and “would be immediately leaked (which it did about 0300, Thursday, 25 October).”

The effect on missile forces was measurable. According to the Archive, 995 ICBMs went on alert after DEFCON 3 took hold, or 99.5 percent of the required force of 1,000 missiles.

Local DEFCONs: Korea

Not every DEFCON is worldwide. The Archive describes one “localized to U.S. forces in South Korea,” called in August 1976 after North Korean soldiers killed U.S. Army officers at the Demilitarized Zone, where they had been trying to trim a tree. A few days later, U.S. Army engineers cut the tree down in “Operation Paul Bunyan,” with B-52s flying in the distance.

The Archive notes another local DEFCON 3 in South Korea in 1979, after President Park Chung Hee was assassinated.

DEFCON 3 on September 11, 2001

The most recent DEFCON change in the public record came on September 11, 2001. The Archive says that after the attacks, “the G.W. Bush administration put U.S. forces on a DEFCON 3 posture.”

The 9/11 Commission Report records the timeline in its notes. Defense Secretary Donald Rumsfeld’s DEFCON 3 decision “was broadcast on the air threat conference call at 10:43.” At 10:45, conferees “were told to ‘hold off’ on Defcon 3, but a minute later the order was reinstated.” Rumsfeld briefed President George W. Bush on the decision at 11:15, according to the report.

Peter’s World’s view

Analysis: Peter’s World’s assessment, based on the sources above.

The DEFCON scale is famous mostly for how rarely it moves. One DEFCON 2 in more than six decades, and a handful of DEFCON 3s, shows that U.S. leaders have treated the higher levels as signals of last resort. The 1973 memo is a reminder that a DEFCON change is also a message: it leaked within hours. Claims online that the country “is at DEFCON 2” or “DEFCON 1” today are not backed by any official source we could find; the levels are not published in real time.

Frequently asked questions

What does DEFCON stand for?

It stands for “defense readiness condition,” the Joint Chiefs of Staff’s five-level scale of military readiness.

What DEFCON level are we at now?

The current level is not published. The National Security Archive says the United States has not gone above DEFCON 3 since 1962.

Has the U.S. ever been at DEFCON 1?

No public record shows DEFCON 1 has ever been ordered. The highest level reached was DEFCON 2, by SAC, in October 1962.

Which is worse, DEFCON 1 or DEFCON 5?

DEFCON 1 is the most serious. The scale counts down, from DEFCON 5 (“Fade Out”) to DEFCON 1 (“Cocked Pistol”).

When was DEFCON created?

The Joint Chiefs created the system in 1959, in Staff Memorandum 833-59, revised in 1961.

Was the U.S. at DEFCON 3 on 9/11?

Yes. The National Security Archive says U.S. forces were put on a DEFCON 3 posture after the attacks of September 11, 2001.

This article was written by Peter with AI assistance and checked against the sources linked. See our AI use disclosure.