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The Phoenix Study U.S. Strategic Air
Command, 1991
In September 1991, less than
year after then defense secretary Dick Cheney ordered a drastic reduction in the
number of nuclear warheads included in various attack options and the number of
targets in the SIOP reduced by 2,500, Strategic Air Command (SAC) completed a
major forces structure study: the Phoenix Study. The study, which was published
only few weeks before President Bush in September 1991 announced sweeping
reductions in U.S. nuclear forces, was the last force structure study conducted
by SAC before the command stood down and was replaced by U.S. Strategic Command
(STRATCOM) in June 1992.
The Phoenix Study was a
compilation of several sub-studies and named after its classification level of
Secret/Phoenix Only. It analyzed the central questions of nuclear war planning:
who should be targeted; what targets should be held at risk; how many aimpoints;
what capability of weapons is needed; how many weapons; what are the special
requirements; how many weapons should be held in reserve; and to what extent is
it necessary to "hedge" against an uncertain future? The answers to these
questions formed the basis of all the other force structure studies conducted in
the 1990s and shaped the Bush administration's nuclear posture review in 2001.
The Phoenix Study
established "rules of thumb," based on historical targeting data, for the
calculation of the number of weapons required to defeat a given number of
installations (targets). The study had roots deep in the Cold War and
essentially summarized SAC's experience from more than 40 years of nuclear
planning. Although many of the details of deleted from the study before it was
released under FOIA, the remaining unclassified sections contain sufficient
information to illustrate how the number of targets in the war plans translate
into number of warheads to achieve a certain degree of damage to individual
targets. This calculation involves five steps in response to the guidance issued
by the president or secretary of defense:
Guidance
Target
Development
Probability
of Arrival (PA)
Aim Points
(Desired Ground Zero)
Probability
of Damage (PD)
In execution of any
given war plan, some warheads will fail to reach their target because of
issues such as technical malfunction, local defenses, and adverse whether
conditions. The Phoenix Study prescribed a rule of thumb of warheads needed
to ensure destruction of each target. The unclassified example given is 20
warheads per 8 targets, depending on delivery platform, needed to ensure
sufficient Probability of Arrival (PA). The number of warheads per target
was different for each type of weapon system, and bombers were considered
three times more vulnerable than ballistic missiles and therefore require
more launch platforms to do the same job. By combining PA with target
characteristics such as hardness and proximity to other targets, the number
of aimpoints needed to guarantee destruction of each target or target group
was calculated. Some aimpoints may be assigned more than one warhead
(layered targeting), but the general assumption in the study was that each
aimpoint -- called Desired Ground Zero (DGZ) -- required one warhead. Each
target (facility) may have more than on DGZ depending on hardness and
geographical size. In the table below these rules of thumbs have been used
to "calculate backwards" to illustrate the ratio between number of targets
and warheads:
Warhead to Target Ratio Estimate
Treaty
framework*
Warheads**
Aimpoints
(DGZ)***
Installations
(targets)****
START I
6000
2400
2500-3500
START II
3500
1400
1450-2000
(START III)
2500
1000
1050-1430
NPR/SORT
2200
880
926-1257
(START IV)
1500
600
630-860
(START V)
1000
400
420-570
*
Treaty framework not in study but included here
for illustrative purpose.
** Based on 1991 Phoenix Study's
example of an average of 20 warheads per 8
aimpoints. *** There are more warheads
than aimpoints because some warheads will fail
to reach their targets for various reasons.
Others warheads are held in reserve. **** There are more
installations than aimpoints because targeting
involves grouping installations in the National
Target Base (NTB) into aimpoints when necessary
where the minimum number of weapons (even a
single warhead) will achieve guidance-directed
Probability of Damage (PD) against individual
installations or groups of installations.
The START I ratio of
6,000 warheads for 2,400 aimpoints roughly corresponds to unofficial
estimates of some 2,500-3,000 targets in SIOP-00. As the number of targets
in Russia continue to decline, the number of aimpoints -- and therefore
required warheads -- also decreases for this portion of the war plan. As a
consequence, the importance of China and other potential enemies on the
overall targeting matrix will increase proportionally and increasingly
influence the composition of the nuclear posture and the war plans. With the
2001 NPR's new focus on so-called capability-based planning, identification
of new targets by military planners in response to vague presidential
guidance will therefore have a proportionally significant impact on defining
future warhead levels and limits on nuclear cuts. Conversely, if the
guidance becomes more precise and requirements for damage expectancy and
scope of target destruction are eased, a "credible" deterrence could be
maintained with much fewer weapons.
Another important
feature of the Phoenix Study is its portrayal of strategic submarines as
playing a much more prominent role in the strike plans than their normal
image of being mainly a retaliatory second-strike force held in reserve. The
study states that the secure reserve force "handles contingencies" and
provides only a "limited restrike capability." Instead the SSBNs are
described as one of the two main pillars in the Triad -- comparable to that
of the ICBM force, which has traditionally been the backbone in the
offensive nuclear strike force. As an unclassified example, the Phoenix
Study only assigns 25 percent of the SSBNs for the strategic reserve force.
This change is a result of the dramatic improvement in the capability of
sea-based ballistic missiles, and of the bomber force becoming less
prominent in the posture. The result is described in the study as a Twin
Triad posture based on the two ballistic missile legs as forming the main
thrust of the nation's deterrent, with the bombers mainly providing back-up.
Indeed, the Phoenix Study concludes that the Secure Reserve Force, which is
mostly SLBMs, "is not a hedge" and that the Twin Triad concept "places the
day-to-day deterrence burden on the two ballistic legs."
The Phoenix Study also
established many of the force planning principles that later influenced the
1993 START II agreement, the 1994 Nuclear Posture Review, and even the 2001
Nuclear Posture Review. To that end the study is an interesting example of
how much of SAC's nuclear planning principles were inherited and perpetuated
by its successor, STRATCOM. These principles include:
The Soviet Union
(Russia) remains the only nation capable of destroying the U.S.; "Handle
the Soviet Union and you can deter all other potential threats;"
The Triad will be more
important in the future because: (1) fewer warheads on fewer
delivery vehicles; and (2) fewer types of both warheads and
delivery vehicles;
The creation of a Twin
Triad, a force structure consisting of ICBMs and SLBMs with bombers acting
primarily as a backup to failure of either of the two;
The Twin Triad
concept uses the bombers to augment attacks by ICBMs and SLBMs and then
is sized to be used in a real hedge role for the first time against the
failure of one of the ballistic legs;
Maintain a "reserve"
of inactive nuclear weapons that can relatively quickly be reconstituted
onto the operational force;
To "hedge" against
uncertainty in the developments in the Soviet Union;
Maintain nuclear
force capability so that allies don't see a need to deploy nuclear
weapons.
(An earlier description of
this document was first published by the Nautilus Institute
Nuclear Strategy Project)
