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Single Integrated Operational Plan

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The Single Integrated Operational Plan (SIOP) represents both a plan and a planning process which specifies how American nuclear weapons would be used in the event of nuclear war. The term SIOP has been replaced by one or more CONPLANs (Contingency Plans), but the term SIOP is still widely used in strategic discussions. [1] By any name, nuclear targeting is a highly classified document, and has been one of the most secret and sensitive issues in U.S. national security policy.

The United States Strategic Command is responsible for the execution of such plans, by whatever name. Current doctrine, however, recognizes that nuclear weapons may not be the most decisive and appropriate means of enforcing critical national policies. Precision-guided munitions, including weapons that can penetrate to deep shelters, may offer non-nuclear alternatives. The kinetic energy of an intercontinental ballistic missile warhead, filled with inert material, may be sufficient to destroy extremely hardened targets.

An enemy that cannot communicate cannot fight, so information operations and electronic warfare are additional means that can be decisive, without any physical effect.

Before the SIOP, nuclear war planning was done independently by the United States Air Force and United States Navy, with limited involvement from the United States Army when it still had long-range nuclear weapons. Until the late Eisenhower Administration, there had been no civilian policy input into nuclear planning, and, when Eisenhower's representative George Kistiakowsky, a key person in designing the first nuclear weapons, reviewed the plans, was shocked by what seemed a mismatch between the policy goals of the use of nuclear effects, and the effects of the weapons selected for specific targets. SIOP is the result of the consolidation of nuclear war planning involving both coordination among the Air Force and Navy, and civilian policy oversight.

Preparation of alternatives

The SIOP (and the differently-named plans that succeeded it) is generated from guidance by the President. The guide is converted by the Secretary of Defense into the Nuclear Weapons Employment Policy (NUWEP) of basic targeting objectives, target lists and operational constraints. The NUWEP is then delivered to the Joint Chiefs of Staff (JCS) and emerges as the Joint Strategic Capabilities Plan (JSCP). The JSCP is then converted into the actual targeting orders, timing, and weapon allocation that comprise the SIOP (and successors) by the USSTRATCOM, which matches weapons effects with the damage intended and the collateral damage to be avoided. The entire process takes up to 18 months. Under President Clinton, the SIOP held four major attack options, 65 limited attack options, and a number of generalised adaptive options for threats originating outside Russia or China.

Nuclear strike targets are listed as the National Target Base (NTB), which is built from an intelligence list of 150,000+ sites across the world. The number of targets in the NTB has varied enormously - from around 16,000 in 1985, 12,500 following the collapse of the Soviet Union, and 2,500 in 1995 before rising to the current list of 3,000 targets. Around 75% of the current targets are in Russia; of these, 1,100 are nuclear weapons sites.

Plan designations

SIOP plans were named after the fiscal year in which they come into effect. This was first officially applied to SIOP-93; prior to that, plans used a two-character alphanumeric designation. A new SIOP is approved every year, although the plan may well be unchanged.

The most recent plan (see below) involving general nuclear war is CONPLAN 8044.

Effects of various strike options

The US nuclear arsenal holds around 7,000 individual warheads. A strong counterforce strike (military targets) using up to 1,500 warheads is estimated to cause approximately 120 million casualties; a limited countervalue strike (civilian targets) of 200 warheads is estimated to cause approximately 50 million casualties.[2]

Blast effects

These estimates are controversial and may be conservative. Ignoring hypothetical long-term effects such as nuclear winter, many of the casualty estimates were based on blast effects alone. Even blast effects are highly dependent on burst altitude, weapon yield, and the geography of the target area. As opposed to the general experience with conventional explosives, the overpressure caused by an explosion is not a simple inverse cube relationship. Instead, the potential of superheated air produces two potential overpressure patterns from a weapon of a given yield, detonated at different altitudes, according to the Mach effect. [3] Essentially, exploiting the Mach effect allows a choice of a small area of very high overpressure, as might be needed for a hardened facility such as a missile silo or command most, or a much larger area of lower overpressure, which would still destroy civilian buildings and many military structures.

High overpressures are essential in counterforce attacks against what may be superhardened targets, while ordinary buildings and factories, the targets of countervalue attacks, would be destroyed by much lower overpressures. Geography and terrain would be factors. For example, the nuclear explosion at Nagasaki was in a valley, where hills partially protected adjacent areas. The main Hiroshima target area was flat and the pressure was roughly symmetrical from the Designated Ground Zero (DGZ) of the Aoki Bridge.

In the early planning, blast was the only factor given serious consideration. [4]. Even with this assumption, which is a vast oversimplification, there is a complex balance among the desired operational and policy effects, the number and yields of weapons available, and the methods and probabilities of accurate delivery.

Certainly in the fifties, the supply of bombs was distinctly limited. Before the SIOP, it appears some SAC thinking was maximizing damage over the most psychologically effective area. Attacking a military installation, if bombs were limited, might lower the probability of destroying the most critical targets, in the interest of affecting a larger area.

Immediate ionizing radiation effects

For these strategic targets, immediate radiation (i.e., straight-line radiation from the fireball) would produce a relatively small proportion of the casualties. Most people in range of lethal radiation would also be in lethal range of blast or thermal effects. While both thermal and ionizing radiation decrease according to an inverse square law, much of the ionization radiation is also attenuated by air.

The "neutron bomb", or enhanced radiation weapon was intended as a tactical weapon that would not be used by the SIOP. Such devices, while still producing enormous blast and heat, produce relatively more immediate ionizing radiation than would the larger-yield weapons delivered as part of SIOP. Enhanced radiation was also a design objective of certain warheads on defensive weapons, intended to damage incoming strategic warheads with X-rays. [5][6]

Electromagnetic effects

It is known that nuclear explosions produce varying intensities of electromagnetic pulse (EMP), which has the potential to damage electronic equipment. Effective power, coverage, and frequencies of the electromagnetic pulse are dependent, at a minimum, on the yield of the nuclear weapon and the altitude of the burst.[7]

While general U.S. planning and engineering documents specify means of EMP protection, [8] no unclassified references suggest that any weapons, targeted under SIOP, are intended principally to produce EMP.

Unexpectedly large fallout pattern from Castle Bravo thermonuclear bomb test

Delayed radiation effects

Delayed and continuing ionizing radiation comes from fallout products of the explosion. In general, the higher the burst altitude, the less fallout; the more surface material that comes in contact with the fireball, the more fallout.

Thermal effects

The casualty estimates in the start of this section did not consider thermal effects, which could cause massive firestorms, killing all blast and immediate radiation survivors within the initial area of effect. [4]

An analysis by Stanford University historian Lynn Eden uses the example of a 300-kiloton weapon bursting, on a clear day, 1500 feet above the Pentagon. Blast would destroy the Pentagon, which is not a hardened facility, and nearby buildings. According to Eden, a much larger area set ablaze by the high levels of thermal energy released by the bomb. "Within tens of minutes, the entire area, approximately 40 to 65 square miles--everything within 3.5 or 6.4 miles of the Pentagon--would be engulfed in a mass fire" that would "extinguish all life and destroy almost everything else."

Since much of the thermal effect is from straight-line infrared radiation, clouds, rain, etc. could attenuate the thermal effect, but this has not been quantified in the open literature. In clear air, thermal energy decreases from the DGZ by an inverse square law, and is not significantly attenuated by dry air.

Another area of complexity would come from target areas that would have be struck by multiple weapons at different Designated Ground Zero (DGZ) points. For example, in an attack on Moscow, the Kremlin and the Special Purpose Command headquarters of the Russian Air Force might be targeted separately. A fire storm centered on each DGZ might eventually merge.


SIOP, and its renamed successors, is most importantly an integrated plan that uses both Air Force and Navy delivery systems; it is "single" only in the sense that it comes out of one planning group. The "plan" actually contains multiple "attack options" that are themselves complex plans.

Early targeting after the Second World War

Strategic nuclear strike plans were developed during the immediate post-World War II period. By the 1950s around 5,500 targets were listed to receive SAC bomber strikes; these targets consisted primarily of industrial sites but included counterforce targets. These plans, primarily by the Air Force, tended to use up the available weapons rather than consider the desired effects. [9] From a 1957 letter from John H. Moore, former director of nuclear planning, air operations branch, United States European Command, Air Force target planning methodology can be inferred "blast damage frame," with such references as "damage to concrete structures" and the requirement for a "high probability of cratering runways." He cited the "destructive and disruptive nature of nuclear weapons" with megaton yields: "the cumulative or ancillary effects may be as great or greater than primary damage." Specifically, he considered delayed radiation but not thermal effects, but called attention to the idea of "bonus" effects,[10] in which the totality of weapons effects would allow lower-yield weapons to achieve the "desired destruction." In the letter to the head of the Atomic Energy Commission, Lewis Strauss, Moore noted that the Pentagon "rigorously suppressed" this study and destroyed all copies.

Prior to the development of SIOP and survivable command & control, President Dwight D. Eisenhower predelegated nuclear release authority to certain senior commanders. [11] There have continued to be Continuity of Nuclear Operations Plans (COOP), which designated enough subordinates who, in the event of the NCA and immediate successors being killed in a "decapitation" attack, could still retaliate. While the details have never been made public, Eisenhower's predelegation, and a Federation of American Scientists summary, give a framework:

Presidential Decision Directive 67 (PDD 67), issued 21 October 1998, relates to enduring constitutional government, continuity of operations (COOP) planning, and continuity of government (COG) operations. The purpose of Enduring Constitutional Government (ECG), Continuity of Government (COG), and Continuity of Operations (COOP) is to ensure survival of a constitutional form of government and the continuity of essential Federal functions. Presidential Decision Directive 67 replaced the Bush Administration's NSD 69 "Enduring Constitutional Government" of 02 June 1992, which in turn succeeded NSD 37 "Enduring Constitutional Government" of 18 April 1990 and NSDD 55 "Enduring National Leadership" of 14 September 1982.[12]

Presidential involvement and start of civilian policy direction

In 1958, George Kistiakowsky, a key Manhattan Project scientist and Science Advisor to the President in the Eisenhower Administration, suggested to the President that inspection of foreign military facilities was not sufficient to control their nuclear weapons. Kistiakowsky, in particular, was concerned with the difficulty of verifying the number, type, and deployment of nuclear-armed missiles on missile submarines, and proposed that the arms control strategy focus on disarmament rather than inspections.[13] He was also concerned with the short warning times available from intercontinental ballistic missile (ICBM) launches, which took away the lengthy decision time available when the nuclear threat came exclusively from manned bombers.

Eisenhower sent Kistiakowsky to Strategic Air Command (SAC) headquarters at Offutt Air Force Base in Nebraska, where he was, at first, rebuffed. At the same time as the early nuclear arms control work, the Chairman of the Joint Chiefs of Staff, General Nathan F. Twining, USAF, sent a memorandum[14] in August 1959, to the Secretary of Defense, Neil McElroy, which suggested that the Strategic Air Command be formally assigned responsibility to prepare the national nuclear target list, and a single plan for nuclear operations. Up to that point, the Army, Navy, and Air Force had done their own target planning. That had led to individual targets being multiply targeted by the different services. The separate service plans were not mutually supporting, as, for example, by the Navy destroying an air defense facility on the route of an Air Force bomber going to a target deeper inland. While Twining had sent the memo to McElroy, the members of the Joint Chiefs of Staff disagreed on the policy during early 1960. [15][16] Thomas Gates, who succeeded McElroy, asked President Dwight D. Eisenhower to decide the policy.[17]

Eisenhower said he would not "leave his successor with the monstrosity" of the uncoordinated and non-integrated forces that then existed. When Kistiakowsky was not given access, Eisenhower sent him back, with a much stronger set of orders, that gave SAC officers the choice to cooperate with Kistiakowsky, or resign.

Kistiakowsky's report, presented on November 29, described uncoordinated plans with huge numbers of targets, many of which would be attacked by multiple forces, resulting in overkill. Eisenhower was shocked by the plans, and focused not just on the creation of the Single Integrated Operational Plan (SIOP), but on the entire process of picking targets, generating requirements, and planning for nuclear war operations. Separate operational plans from the Air Force and the Navy were combined to form the foundation of the SIOP.

The first SIOP

The first plan, following the White House policy guidance, was developed in 1960, consisting of a list of targets (the National Strategic Target List, or NSTL) and the assets to be used against each target. This first SIOP was extensively revised by a team at the RAND Corporation to become SIOP-62, a massive strike with the entire US arsenal of 3,200 warheads against the USSR, China and Soviet-aligned states. In 1963 the Kennedy administration ordered Robert McNamara to revise this plan, resulting in SIOP-63 — a strong counterforce strategy with a number of options. It was with SIOP-63 that the 'no first use' policy became implicit.

The counterforce approach recognized three missions, sometimes called Alpha, Bravo, and Romeo after the phonetic alphabet symbols for the different goals. The specific plans included options for combining the missions:[18]

  • Alpha: neutralize the enemy's capability to conduct an atomic attack
  • Bravo: blunt the enemy's ability to produce materials to support military operations
  • Romeo: retard the enemy's ability to move into friendly territory, primarily Western Europe

From the limited documents available, it did not seem fully realized that to destroy a hardened reactor or command facility, which would be part of Mission Alpha, high overpressures would be needed.

An early SIOP, however, had little flexibility, treating all Communist countries as a uniform bloc. Document JCS 2056/220 expressed the concerns of U.S. Marine Commandant David Shoup that the 1961 draft was inconsistent with an 1959 NSC policy guidance paper approved by Eisenhower. [19] Shoup was especially concerned with language in the draft SIOP that said
The United States should utilize all requisite force against selected targets in the USSR--and as necessary in Communist China, European Bloc and non-European bloc countries--to attain the above objectives. Military targets in Bloc countries other than the USSR and Communist China will be attacked as necessary.

The National Security Archive commentary reports that Marine Commandant David Shoup asked USAF/SAC Commander Thomas Power "...what would happen if Beijing was not fighting; was there an option to leave Chinese targets out of the attack plan? Power was reported to have said that he hoped no one would think of that "because it would really screw up the plan"--that is, the plan was supposed to be executed as a whole. Apparently Shoup then observed that "any plan that kills millions of Chinese when it isn't even their war is not a good plan. This is not the American way.""

Counterforce migrates to deterrence and warfighting

Counterforce dominated SIOP plans until SIOP-5 in 1976 when the plan became a model for deterrence based on Nixon's NSDM-242 (sometimes called the 'Schlesinger Doctrine' after then-Secretary of Defense, James Schlesinger).[20] The ever-expanding target lists were split into classes of targets, with a wider range of plans matching strikes to political intentions from counterforce to countervalue, or any mix/withhold strategy to control escalation. Schlesinger described the doctrine as having three main aspects:

  1. The National Command Authority or its successors should have many choices about the use of weapons, always having an option to escalate.
  2. Targeting should make it very explicit that the first requisite is selective retaliation against the enemy's military (i.e., tailored counterforce).
  3. Some targets and target classes should not be struck, at least at first, to give the opponent a rational reason to terminate the conflict. Reduced collateral damage was another benefit of this "withhold" method.

The SIOP policy was further modified during the Carter presidency under Presidential Directive 59, a key section of which stated

The employment of nuclear forces must be effectively related to operations of our general purpose forces. Our doctrines for the use of forces in nuclear conflict must insure that we can pursue specific policy objectives selected by the National Command Authorities at that time, from general guidelines established in advance. (S)[21][22]
These requirements form the broad outline of our evolving countervailing strategy. To meet these requirements, improvements should be made to our forces, their supporting C3 and intelligence, and their employment plans and planning apparatus, to achieve a high degree of flexibility, enduring survivability, and adequate performance in the face of enemy actions. The following principles and goals should guide your efforts in making these improvements. (S)

In other words, PD59 explored a "warfighting" doctrine that suggested that nuclear plans might change during a war, and that nuclear weapons were to be used in combination with conventional weapons. Carter's Secretary of Defense, Harold Brown, emphasized selective counterforce, but also explicitly threatened the Soviet leadership themselves. Major improvements in U.S. command, control, communications and intelligence (C3I), including making elements survivable during a nuclear war, were instituted to make the PD-59 doctrine feasible.Cite error: Closing </ref> missing for <ref> tag The idea of effective strategic defense was a potential disruption to the existing balance of Mutual Assured Destruction, even with its "warfighting" refinements.

Renaming and refocusing

On 1 March 2003, the SIOP was renamed "OPLAN 8022", and later CONPLAN (contingency plan) 8022.[23] It went into deployment in July 2004, but it was reported cancelled in July 2007. It may have been superseded by an expanded CONPLAN 8044 (see below).

Another set of "Global Strike" plans include a jointly coordinated a nuclear option, intended for other than the general nuclear war situations, principally with Russia but possibly also with China, postulated in OPLAN 8022. Global Strike plans are codified in CONPLAN 8044. [24]

Executing the SIOP

In the United States, the decision to use nuclear weapons is vested in the National Command Authority (NCA), composed of the President of the United States and the United States Secretary of Defense or their successors. The President alone cannot order an attack. The ordering of use, communication of orders, and the release of nuclear weapons is governed by the two-man rule at all times.
Deputy silo commander key in Minuteman ICBM silo. Commander's key is too far away to be turned by the same person
No one person ever can take such an action. All military personnel that participate in loading, arming, or firing weapons, as well as transmitting launch orders, are subject to the Personnel Reliability Program (PRP).

If the NCA decides that the United States must launch nuclear weapons, they will direct the Chairman of the Joint Chiefs of Staff (CJCS) to do so. At the NCA/JCS level, the orders will be to execute SIOP strike options, broken into Major Attack Options (MAOs), Selected Attack Options (SAOs), and Limited Attack Options (LAOs). Individual countries or regions can be included in or withheld from nuclear attacks depending on circumstances. The CJCS in turn will direct the general officer on duty in addition to one other officer on duty in the National Military Command Center (NMCC) at the Pentagon to release an Emergency Action Message (EAM) to all nuclear forces; another officer will validate that order. [25] Additionally, the message will go to the Alternate National Military Command Center (ANMCC),[26] located in Raven Rock Mountain, Pennsylvania, and also to an airborne command post, either the presidential National Airborne Operations Center (NAOC) or the military E-6B TACAMO If the NMCC is destroyed by a first strike, either the ANMCC, NAOC or TACAMO[27] can issue the orders to execute the SIOP.

E-6B strategic command aircraft

As the orders go down the chain of command, always subject to the two-man rule, intermediate headquarters, and eventually the nuclear delivery platforms themselves, will receive Emergency Action Messages (EAM) to arm or launch weapons. For most modern weapons, the EAM will also include code(s) for Permissive Action Links (PAL).

At a minimum, a PAL code will actually arm a weapon for release. The circuitry controlling the PAL is deliberately positioned inside the warhead such that it cannot be reached without disabling the weapon, at a minimum, to a level that would require a full factory-level rebuild. There may be separate PAL codes for arming and launch. Some weapons have "dial-a-yield" functions that allow the power of the nuclear explosion to be adjusted from minimum to maximum yield. Most weapons have additional arming circuitry that, even if a valid launch code is entered, will not arm the warhead unless the weapon senses that it has been released on an expected delivery path. For example, the first steps of the final arming process for a ballistic missile depend on physical characteristics of the weapon release, such as the acceleration of a rocket launch, zero-gravity coasting, and various physical aspects of hypersonic reentry into the atmosphere. A gravity bomb dropped from an aircraft will detect the altitude of release and the decreasing altitude as it falls.

British/NATO involvement

At a NATO level, an agreement to use nuclear weapons envisages the United Kingdom participating in the SIOP. The plan integrates the nuclear capabilities of the "triad" composed of bombers with intercontinental range, land-based intercontinental ballistic missiles (ICBM) and sea-based submarine-launched ballistic missiles (SLBM).

While the United Kingdom's nuclear deterrent - four Trident Vanguard class submarines - are strictly under UK national control, they do have two distinct roles. The first is part of a UK-only retaliatory response to a nuclear attack, whether a full strategic strike involving all of the Royal Navy's Trident submarines, or a limited tactical strike. The second role is one in which the Royal Navy participates in the SIOP, in effect becoming non-distinct from the U.S. Navy's Trident submarines. This role was to be part of a NATO response to a Soviet nuclear strike.

The Royal Navy's contribution to the SIOP shows the power of the nuclear arsenal committed to the plan. The four Vanguard submarines could strike a maximum of 512 separate targets; this is equivalent to 7% of the total U.S. nuclear strike capacity.


  1. Burr, William, ed. (13 July 2004), The Creation of SIOP-62: More Evidence on the Origins of Overkill, George Washington University National Security Archive
  2. National Resources Defense Council (June 2001), The U.S. Nuclear War Plan: A Time for Change
  3. Sublette, Cary (Version 2.14: 15 May 1997), Chapter 5.0 Effects of Nuclear Explosions, section 5.4 Air Bursts and Surface Bursts, Nuclear Weapons Frequently Asked Questions
  4. 4.0 4.1 Burr, William, ed. (14 January 2004), "It Is Certain There Will be Many Firestorms": New Evidence on the Origins of Overkill, George Washington University National Security Archive
  5. Spartan, 27-Jan-2003
  6. Sublette, Cary (Version 2.14: 15 May 1997), Chapter 4.0 Effects of Nuclear Explosions, section Radiation Case, Nuclear Weapons Frequently Asked Questions
  7. Sublette, Cary (Version 2.14: 15 May 1997), Chapter 5.0 Engineering and Design of Nuclear Weapons, section 5.5 Electromagnetic Effects, Nuclear Weapons Frequently Asked Questions
  8. United States Department of Defense (17 July 1998), High-altitude electromagnetic pulse (HEMP) protection for ground-based C4I facilities performing critical, time-urgent missions, MIL-STD-188-125-1
  9. Moore, John H. (14 February 1957), Letter from Captain John H. Morse, Special Assistant to the Chairman, Atomic Energy Commission, to Lewis Strauss, Chairman, Atomic Energy Commission, in Burr, William, "It Is Certain There Will be Many Firestorms": New Evidence on the Origins of Overkill, George Washington University National Security Archive, Dwight D. Eisenhower Library, Records of Special Assistant for National Security Affairs, NSC Series, Briefing Notes Subseries, box 17, Target Systems (1957-1961)
  10. Kahn, Herman (1968), On Escalation: Metaphors and Scenarios, Penguin
  11. Burr, William, ed. (18 May 2001), First Declassification of Eisenhower's Instructions to Commanders Predelegating Nuclear Weapons Use, 1959-1960, George Washington University National Security Archive
  12. Enduring Constitutional Government and Continuity of Government Operations (U), Federation of American Scientists, 21 October 1998, Presidential Decision Directive PDD-NSC-67
  13. , Space Policy Project (summary of Foreign Relations of the US, text not online), Foreign Relations of the United States 1958-1960, vol. National Security Policy; Arms Control and Disarmament, Volume III, Washington, DC: US Department of State (summary by Federation of American Scientists), 1961, FRUS58
  14. Twining, Nathan F. (20 August 1959), Document 2: J.C.S. 2056/131, Notes by the Secretaries to the Joint Chiefs of Staff, enclosing memorandum from JCS Chairman Nathan Twining to Secretary of Defense, "Target Coordination and Associated Problems,", The Creation of SIOP-62: More Evidence on the Origins of Overkill, George Washington University National Security Archive. Retrieved on 2007-09-22
  15. Twining, Nathan F. (5 October 1959), Document 3A: JCS 2056/143, Note by the Secretaries to the Joint Chiefs of Staff, 5 October 1959, enclosing Memorandum for the Joint Chiefs of Staff, "Target Coordination and Associated Problems,", The Creation of SIOP-62: More Evidence on the Origins of Overkill, vol. Electronic Briefing Book No. 130, George Washington University National Security Archive. Retrieved on 2007-09-22
  16. Burke, Arleigh (30 September 1959), Document 3B: attached memorandum from Chief of Naval Operations, The Creation of SIOP-62: More Evidence on the Origins of Overkill, George Washington University National Security Archive
  17. McKinzie, Matthew G. & Thomas B. Cochran (2001), Chapter Two: The Single Integrated Operational Plan and U.S. Nuclear Forces, The U.S. Nuclear War Plan: A Time for Change, National Resources Defense Council
  18. Baldwin, William C., Strategic Nuclear Weapons and Nuclear Engineering, 1953-1960, A History of the U.S. Army Engineer Studies Center 1943-1982, U.S. Army Engineer Studies Center
  19. Shoup, David (11 February 1961), Document 25: Note by the Secretaries to the Joint Chiefs of Staff on Review of the NSTL/SIOP-62 and Related Policy Guidance, JCS 2056/220,, The Creation of SIOP-62: More Evidence on the Origins of Overkill, George Washington University National Security Archive
  20. Cimbala, Stephen J. (September-October 1984), "War-Fighting Deterrence and Alliance Cohesiveness", Air University Review
  21. In U.S. classified documents, paragraphs and titles may have classification markings such as (S) for SECRET, (U) for UNCLASSIFIED, (C) for CONFIDENTIAL, and (TS) for TOP SECRET. Any of these letters may be followed with one or more control markings (e.g., EYES ONLY, HANDLE THROUGH COMINT CHANNELS ONLY) or code words/nicknamesd (e.g., UMBRA, POLO STEP)
  22. Carter, Jimmy (1980), Presidential Directive 59, Nuclear Weapons Employment Policy, The White House
  23. U.S. Nuclear Weapons Guidance, The Nuclear Information Project (joint with Federation of American Scientists), 3 January 2008
  24. Kristensen, Hans M. (15 March 2006), Global Strike: A Chronology of the Pentagon’s New Offensive Strike Plan, Federation of American Scientists
  25. Pike, John, National Military Command Center,
  26. "Alternate National Military Command Center", New York Times
  27. "B" model carrying a battlestaff only
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