DEFCON

The defense 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 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.

Levels
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:

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.

History
After 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 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 two conditions: "Defense Emergency" and the highest, "Air Defense Emergency" ("Hot Box" and "Big Noise" for exercises).

For much of the Cold War, American ICBM sites were at DEFCON 4, rather than 5.

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.

Yom Kippur War
The U.S. Armed Forces were at DEFCON 3 status during the 1973 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.

Operations
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.

Different branches of the U.S. Armed Forces (like the U.S. Army, U.S. Navy, Air Force) and different bases or command groups can be activated at different defense conditions. There is no single DEFCON status for the country, as they are decided on an individual basis by respective branches of the military.

In other media

 * DEFCON was referenced in the title of the film Def-Con 4 and used in the films WarGames, Thirteen Days, Watchmen, Independence Day, The Sum of All Fears, Crimson Tide, Armageddon, Mars Attacks! and Olympus Has Fallen.
 * 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.