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An Explanation of Nuclear Weapons Terminology
by Steven Starr
Nuclear Age Peace Foundation, December 2007



Discussions of nuclear weapons and the policies which guide them often utilize terminology which lacks standardized definition. Much of the nuclear jargon consists of words or phrases which are essentially descriptive terms whose meaning is generally agreed upon, but in fact do not have precise technical definitions in any military or civilian dictionaries. Such imprecision in language has created confusion among those trying to comprehend nuclear issues and has even hindered the process of negotiation among nations.

This problem of imprecision exists for a variety of reasons. Some terms may not be listed in the U.S. Department of Defense (DOD) online Dictionary of Military Terms (see [formats local on ratical (accessed 07/18/15): PDF, Excel - Terms & Definitions, Excel - Acronyms & Definitions]) because they refer to policies, such as “launch-on-warning”, which the U.S. government does not wish to acknowledge or discuss. Other terms, such as “high-alert status”, “hair-trigger alert” and “de-alerting”, may be regarded as useless by military officers who would wish to regard their forces as always “alert”.

Although civilians and the military may approach the use of such terminology from different perspectives, it is important that they at least be able to understand each other when conversing. A lack of precise terminology will continue to plague discussions of nuclear policy until adequate definitions are finally agreed upon by all parties.

The U.S. recently employed imprecision in terminology as a tactic during the 2007 General Conference on Disarmament at the United Nations, when it announced, “The fact is that U.S. nuclear forces are not and have never been on ‘hair-trigger alert’.” By repeatedly using the term “hair-trigger” (which lacks technical meaning but is commonly used to describe fire-arms and bad tempers), the U.S. deliberately muddied the semantic waters in an attempt to avoid serious discussion about the true status of its nuclear arsenal[1].

The U.S. apparently chose this strategy because the governments of New Zealand, Sweden, Switzerland, Nigeria and Chile had put forward a Resolution to the General Assembly which called for the removal of all nuclear weapons from “high-alert status”[2]. This left many of the delegates at the U.N. scrambling for a means to decipher exactly what was being debated.

Because I had been asked to speak in support of the New Zealand Resolution[3], I decided to present the delegates with definitions for commonly used nuclear terms. I found, however, that very few published definitions are available for such terms, and so I instead developed a list of what I believe are valid explanations for commonly used nuclear jargon (copied below). It is my hope that eventually all these words and phrases can be assigned standardized definitions usable by both civilians and military authorities.

“Operational”, “Active” and “Deployed” nuclear weapons

  • Fully functional nuclear weapons which are either mated to delivery systems or available for immediate combat use.
  • There are about 11,800 operational/active/deployed nuclear weapons in the global nuclear arsenal (mostly U.S. and Russian).

Note: The DOD has a rather confusing definition for “Deployed Nuclear Weapons” available at

“Reserve” or “Inactive/Responsive” nuclear weapons

  • Nuclear weapons not immediately available for combat. They are kept in long-term storage as spares, as a source of parts for remanufacture or the manufacture of other weapons, or held in reserve as a responsive force that may augment deployed forces. These weapons can lack some component which renders them inoperable unless that component is replaced.
  • There are 13,500 reserve nuclear weapons in the U.S. and Russian arsenals. Should they choose to do so, the U.S. and Russia could use these reserves to essentially double the number of operational nuclear weapons in their arsenals within a relatively short period of time.

Note: The great irony of “arms control” negotiations is that the reductions which have occurred through the SALT, START and SORT treaties have focused only upon the destruction of missile silos and submarine launch tubes – not on eliminating nuclear warheads or even missiles, but only upon reducing the total number of operational delivery systems. Consequently, as the delivery systems were eliminated, many of the warheads were taken out of active service and placed in the “reserve” arsenals of the U.S. and Russia.

“Low-yield” nuclear weapons

  • Generally refers to simple fission weapons, first described as “atomic bombs”, which have a nominal explosive power of about 15 kilotons, roughly the size of the bombs dropped on Hiroshima and Nagasaki. These are the type of weapons which would be made by emerging nuclear weapon states such as India and Pakistan or by terrorists (using Highly Enriched Uranium).

“Tactical” nuclear weapons

  • This is an older term which is no longer useful in describing the explosive size of nuclear weapons (many modern versions of these weapons can have large yields). “Tactical” now infers that the weapon is used for limited, or “theater” military operations, but not long-range intercontinental missions. Thus, the term “non-strategic weapon” is more appropriate.

“Strategic” nuclear weapons

  • Often referred to as “high-yield” or “thermonuclear” nuclear weapons. The first generations of these weapons were called “hydrogen bombs” because they used (and still use) atomic bombs as triggers to generate enough heat to cause the nuclear fusion of hydrogen atoms (fusion is the same process which powers the Sun). Most modern thermonuclear weapons are 20 to 50 times more powerful than the Hiroshima-size bombs, although weapons more than 1000 times as powerful still exist in the global nuclear arsenal.
  • Strategic nuclear weapons generally have an explosive power of at least 100 kilotons yield, i.e. 100,000 tons of TNT.
  • There are 7200 strategic nuclear weapons in the global nuclear arsenal.
  • For a detailed explanation of nuclear weapon design, look it up at Wikipedia, see

”High-alert status” or “Launch-ready alert”

  • Commonly refers to intercontinental ballistic missiles (ICBMs) or submarine launched ballistic missiles (SLBMs) armed with strategic nuclear warheads, able to be launched in a matter of 15 minutes or less. Can include any missile or weapon system capable of delivering a nuclear warhead in this time frame.
  • Maximum flight time of 30 minutes or less for U.S. and Russian ICBMs and SLBMs to reach their targets.
  • Total time required to launch high-alert ballistic missiles and have their nuclear warheads reach their targets = 45 minutes or less. With high-alert nuclear forces a nuclear war can be ordered, launched and completed in less than one hour.

Note: A definition of high-alert requires no specific explosive power of the weapon on the missile, but in general, most high-alert missiles are armed with strategic nuclear weapons with yields equal to or greater than 100 kilotons. The U.S. and Russia have for decades possessed solid fuel ICBMs and SLBMs capable of being launched in 2 or 3 minutes. The U.S. “Minuteman” ICBM earned its name for its quick-launch capability.

Nuclear forces now at “High-alert status”

A large fraction of the following forces, including at least 2600 to 3500 strategic nuclear warheads:

  • U.S. land-based Intercontinental Ballistic Missiles = 1050 strategic nuclear warheads
  • 4 U.S. Trident submarines kept at “hard alert”, carrying a total of 600 high-yield warheads
  • Russian land-based Intercontinental Ballistic Missiles = 1843 strategic nuclear warheads
  • Russian nuclear subs in port (virtually all year) carrying a total of 624 high-yield warheads

“De-alerting” nuclear weapons

  • De-alerting prevents the rapid use of nuclear weapons by introducing physical changes to nuclear weapon systems which lengthen the time required to use the nuclear weapons in combat. Such changes are made in order to allow more time for rational decision-making processes to occur and hopefully avoid nuclear conflict.
  • De-alerting is a reversible process which can be used to rapidly implement existing arms control agreements ahead of schedule. In other words, arms control agreements create a timetable to introduce irreversible reductions of weapon systems, but these changes generally occur incrementally over the course of a number of years. De-alerting can be utilized to rapidly implement the entire range of negotiated reductions in a reversible fashion (which over time are then made irreversible), thereby bringing the benefits of the negotiated reductions into being much more rapidly.
  • Examples of de-alerting:
    1. Placing large, visible barriers on top of missile silo lids which would be difficult to rapidly remove,
    2. Removing or altering firing switches of missiles to prevent rapid launch,
    3. Removing warheads from missiles and storing them in a separate, monitored location.
  • De-alerting may require negotiations and verification procedures in order to accomplish symmetrical force reductions on both sides. However, de-alerting can occur rapidly if sufficient political will exists, e.g., the 1991 Bush and Gorbachev Presidential Nuclear Initiatives.
  • De-alerting nuclear forces would prevent a false warning from triggering a retaliatory nuclear strike (accidental nuclear war) via launch-on-warning policy (see next definition).

Note: It would be worthwhile to define separate stages of de-alerting which would refer to specific increments of time required to return a weapon system to high-alert status. For example, Stage 1 de-alerting would require 24 hours to bring the weapon system back to high-alert status; Stage 2 de-alerting would require a week; Stage 3 de-alerting would require a month or more to reconstitute the weapon system.

Launch-on-Warning (LoW) policy

  • The Cold War policy of launching a retaliatory nuclear strike to a perceived nuclear attack only on the basis of electronic Early Warning System data before the reality of the perceived attack is confirmed by nuclear detonations from the incoming warheads.
  • Under LoW policy, a false warning misinterpreted as a true attack could trigger a retaliatory nuclear strike, and thus cause an accidental nuclear war.
  • Under LoW policy, the 30 minute (or less) flight time of ballistic missiles dictates that only a few minutes are available to evaluate Early Warning System data and act upon it before the arrival of incoming nuclear warheads. If the attack warning is accepted as accurate, top U.S. or Russian military commanders would contact their President to advise him, and the president would then be allowed only a few minutes to decide whether or not to launch a nuclear retaliatory strike – before the perceived attack arrives.
  • Launch-on-Warning capability can be eliminated by introducing physical changes to nuclear weapon systems which prevent their rapid use (de-alerting). In other words, Launch-on-Warning requires high-alert forces that can be launched in 15 minutes or less. If you remove nuclear forces from high-alert, you CANNOT Launch-on-Warning.
  • Launch-on-Warning policy can be ended overnight by Presidential decree.
  • By replacing LoW policy with a policy of Retaliatory Launch Only After Detonation (RLOAD), a false warning misinterpreted as a true attack could no longer cause an accidental nuclear war.

For a more detailed analysis on LoW and its alternatives, see “Replace Launch on Warning Policy” by Phillips and Starr at

Note: The U.S. presently maintains that it does not operate under the policy of Launch-on-Warning (LoW). Although the U.S. DOD Dictionary of Military Terms lacks a definition for LoW, in 2007 it did define Launch Under Attack (LUA) – with a definition exactly the equivalent to the commonly used definition of LoW! Perhaps we should ask the U.S. if it operates under LUA? Furthermore, Russian military experts (writing in English) use LUA to mean something significantly different than the 2007 U.S. DOD definition. Russian usage of LUA refers to the delivery of a retaliatory nuclear strike “in response to an actually delivered strike”, i.e. after nuclear detonations have been confirmed (see Valery Yarynich, C3: Nuclear Command, Control, Cooperation, Washington, D.C.: Center for Defense Information, 2003, pp. 28-30.)

Launch-on-Warning (LoW) capability

  • Early Warning Systems (EWS), high-alert nuclear-armed ballistic missiles, and nuclear command and control systems, all working together, provide the U.S. and Russia the capability to Launch-on-Warning.

Launch-on-Warning (LoW) status

  • The combination of Launch-on-Warning capability with Launch-on-Warning policy has created what is commonly referred to as Launch-on-Warning status.
  • LoW capability + LoW policy = LoW status

Note: This is my own opinion and definition. I felt obligated to come up with the explanation for “LoW status” because the term has often been used by non-governmental observers to describe the strategic nuclear forces of the U.S. and Russia.

“Hair-trigger alert”

  • “Hair-trigger alert” is a figurative term sometimes used to describe strategic nuclear weapons at Launch-on-Warning status and in particular the condition of U.S. and Russian strategic nuclear arsenals, see “A Rebuttal of the U.S. Statement on the Alert Status of U.S. Nuclear Forces” by Bruce Blair at
  • “Hair-trigger alert” has been used to confuse the debate about the status of nuclear arsenals. For purposes of diplomacy, it may be wise to use non-figurative and more technical terms to describe nuclear policy and nuclear weapon systems.


  1. The text of the Oct. 9, 2007, U.S. statement at the U.N. can be viewed at Two authoritative rebuttals to the U.S. Statement are posted on the internet at the website of the Lawyers Committee on Nuclear Policy, see: These include, “A Rebuttal of the U.S. Statement on Nuclear Weapons Alert, Dismantlements and Reductions”, by Dr. Hans M. Kristensen, the Director of the Nuclear Information Project at the Federation of American Scientists, see and, “A Rebuttal of the U.S. Statement on the Alert Status of U.S. Nuclear Forces”, by Dr. Bruce Blair, President of the World Security Institute, see

  2. The Resolution, “Decreasing the operational readiness of nuclear weapons systems,” A/C.1/62/L.29 (GA 62/36), 17 October 2007, passed by the vote of 124 to 3, with only the U.S., the U.K. and France voting against it. The U.S. voted against the Resolution because it said the Resolution was “meaningless”.

  3. Our Oct. 16th panel, which discussed the Operational Status of Nuclear Weapons, also included speeches by the Ambassadors of New Zealand and Sweden, and a presentation by John Hallam of Australia, with Ms. Rhianna Tyson of the Global Security Institute as moderator.

  4. Steven Starr is an independent writer who has been published by the Bulletin of the Atomic Scientists and the Moscow Institute of Physics and Technology Center for Arms Control, Energy and Environmental Studies. He recently retired from the medical profession to work as an educator and consultant on nuclear weapons issues.

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