THE SOVIET ATTACK SUBMARINE FORCE AND WESTERN SEA LINES OF COMMUNICATION

• Document Type: FOIA
• Collection: CIA Analysis of the Soviet Navy
• Document Number (FOIA) /ESDN (CREST): 0005499486
• Release Decision: RIPPUB
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• Document Page Count: 21
• Document Creation Date: June 19, 2017
• Document Release Date: June 19, 2017
• Case Number: SC-2007-00006
• Publication Date: April 1, 1979

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Assessment
Center
The Soviet Attack Submarine
Force and Western
Sea Lines of Communicationn
An Intelligence Assessment
Information as of September 1978 has been used
in preparing this report.
The author of this paper is
Office of Strategic
Research. Comments and queries are welcome
This assessment has been coordinated with the Offices
of Scientific Intelligence Wea ns Intelligence,
and Economic Research.
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"-Staid,
SR 79-10038
April 1979
AR 70-14
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Foreword
The Director of Central Intelligence has reviewed this
pstudy
and makes the following introductory comments.
There are two basic elements to the study. The first is:
What are the Soviet intentions with respect to attempt-
ing sea denial in the North Atlantic? The second is:
What are the Soviet ca abilities to execute sea denial if
they decided to do so?
With respect to intentions, I believe it is clear that
planners on both the Warsaw Pact and NATO sides
basically expect a short war. I therefore agree with the
study that sea denial operations in the North Atlantic
are not a high priority item for Soviet naval efforts in
the initial stages of either a nuclear or conventional
war between the Warsaw Pact and NATO. At the
same time, in advance of both World War I and World
War H, everyone expected that there would be a short
war. In advance of each of these wars the Germans did
not make explicit preparations for a war of sea denial
and yet were forced into it by events. I therefore believe
there is a high probability that if a war between the
Warsaw Pact and NATO became an extended conven-
tional conflict, the naval side of the war would turn into
a protracted campaign of sea denial versus sea control
in the North Atlantic. In short, there is reason to
believe that this is not the Soviet intent today, but
reason to be concerned that it may well become that
intent if a war in which seaborne supply is a factor does
evolve
This means that the important part of the study is that
concerning Soviet capabilities. Clearly if we establish
that the Soviets do not have a substantial capability to
conduct a sea denial campaign, this would have
important implications. This study attempts to show
Soviet capabilities given a wide range of assumptions
governing the use of the USSR's submarines. It
provides the reader with some indications of the
sensitivity of various assumptions. There is work to be
done, however, on assessing Soviet capabilities against
varying assumptions about Western ASW and ship-
111
ping strategies. In my view, the recent intelligence
assessment that Soviet submarines carry substantially
smaller loads of torpedoes than had previously been
assumed is a major factor militating against a Soviet
capability to exercise sea denial. The study assesses
Soviet capabilities using as measures of effectiveness
numbers of ships sunk and cargoes lost, percentage
losses of NATO-flag ships over 6,000 GRT, and
percentage losses of required economic and military
cargoes. These measures suffer from imprecision and
much more work remains to be done in this area, most
of it by the Department of Defense, which has data on
shipping requirements and availabilities.
With the cooperation and contribution of the Depart-
ment of Defense, we plan soon to undertake an
Interagency Intelligence Memorandum to assess on a
broader basis the interdiction capabilities of the Soviet
Navy against NATO sea lines of communication in
wartime.
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Stansfield Turner
...8tter<
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The Soviet Attack Submarine
Force and Western
Sea Lines of CommunicationP
Key Judgments
This study assesses the intention and the capability of
the Soviets to disrupt the flow of Western military and
economic shipping in a protracted conventional war
with NATO by conducting submarine attacks on
merchant ships at sea. We conclude that the Soviets
would assign only a few attack submarines for use
against shipping early in a war. They would probably
assign more to interdiction if the conventional phase of
a NATO-Pact war were prolonged and if the Soviets
perceived that Western carriers, amphibious task
forces, and submarines no longer posed any threat
With their large fleet of general purpose submarines,
the Soviets would have an inherent capability to
threaten NATO's sea communications if they chose to
concentrate their efforts on this task. But even if they
realigned their priorities in favor of interdiction,
several factors would constrain their ability to main-
tain a large submarine presence in the North Atlantic:
the long transits, the small torpedo capacity of many of
the submarines, the lack of replenishment opportuni-
ties outside home waters, the turnaround time between
patrols, and combat attrition.
'tterA,L
Important to the success of a Soviet interdiction
campaign would be the ability to discriminate between
ships loaded with vital military equipment and those
carrying economic support cargoes. The Soviets' satel-
lite-borne ocean surveillance systems might reduce the
time their submarines would have to spend searching
for targets. These systems are vulnerable to counter-
measures, however, and in any case their data would be
generally suitable only for locating ships at sea, not for
identifying specific ships. As long as economic shipping
continued?as it almost certainly would in a prolonged
conflict?ships carrying economic cargoes would prob-
ably be intermixed with ships carrying military equip-
ment. Unable to discriminate between them, the
Soviets would have to attack ships chosen at random?
further diluting their capability to the
military resupply of NATO.
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Contents
Page
Foreword iii
Key Judgments
Preface ix
The Soviet View of Interdiction 1
Competing Requirements for Submarines 2
Capability of Soviet Attack Submarines in the Atlantic Ocean
and Contiguous Seas 3
Availability for Operations 3
Torpedo Reloads 5
Time on Station 5
Combat Attrition 6
Weapons Effectiveness 6
Target Acquisition 7
NATO Sealift Resources 8
Outlook 8
Appendix
Analysis of Soviet Interdiction Capabilities 11
Figures
1.
Submarine Transit Distances to Possible Wartime Sea Lane 6
2. Cumulative Western Ship Losses
13
3. Cargoes Delivered and Cargoes Lost in a Hypothetical
All-Out Interdiction Campaign 14
Tables
1.
Fleet Distribution of Soviet Attack Submarines, September 1978 4
2. NATO Losses in a 120-Day Interdiction Campaign:
Three Scenarios 12
3. NATO Losses in a 120-Day Interdiction Campaign:
Variations on the Basic Model 16
vii ar<
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Preface
Debate in the United States over naval strategy and
the Navy's shipbuilding program has focused interest
on the ability of the USSR's large fleet of attack
submarines to interdict main Western sea lines of
communication. Analysts in the US Intelligence Com-
munity have taken differing points of view on this issue
and have formed markedly different judgments of the
capabilities and intentions of the Soviet Navy in its
tential employment of submarines for interdiction.
This assessment describes one view of the interdiction
problem. After briefly placing interdiction in the
broader context of Soviet naval policy, it focuses on
Soviet capability to disrupt the resupply of NATO's
Central Region by conducting submarine attacks on
merchant shipping in the North Atlantic. Soviet
capability to cut NATO's sea communications with
Norway is outside the scope of this paper.
the assum tions used in this model and the results
obtained
The paper makes several related assumptions: that
Soviet submariners could not identify ships carrying
war materiel in a stream of shipping, that NATO
logistic managers would distribute those high-value
ships among similar ships carrying less valuable
economic cargoes, and that this shipping strategy
would distribute losses at random among the total
cargoes shipped. Our analysis did not include the
beneficial effects of convoying, which could reduce
losses to escorted merchant ships and increase losses to
the submarines.
For this study, interdiction is defined as the disruption
of merchant shipping (of military or commercial
cargoes, or both) in the open ocean. The definition
excludes warships, military logistic ships, and
amphibious landing forces.
A model was used in the analysis of Soviet capabilities
in several possible scenarios. The appendix describes
ix
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The Soviet Attack Submarine
Force and Western
Sea Lines of Communication
The Soviet View of Interdiction
The Soviets hope to disrupt Western shipping by
launching air and missile strikes against ports, con-
ducting submarine attacks on merchant ships on the
high seas, and mining heavily traveled waters. While
we recognize that they could?and probably would?
use all three forms of interdiction, this paper discusses
only their capabilities to conduct submarine attacks on
merchant ships in the North Atlantic
The most effective way to disrupt shipping, the Soviets
believe, is to attack the land-based facilities upon
which it depends. Soviet criticism of Germany's failure
in World War II to carry out "massed and systematic"
strikes against British ports suggests that they would
try to disrupt port operations in the conventional and
limited nuclear phases of war as well as in a nuclear
conflict. To be effective in a nonnuclear war, however,
such attacks would require large-scale and repetitive
bombing. The Pact probably would not make many
bombers available for attacks on ports unless it had
won the battle for air superiority and had destroyed
NATO tactical nuclear strike forces.
The Soviets regard mining as useful in a conventional
war because clearing minefields imposes an additional
strain on enemy navies, and precautions against them
lengthen the time that rnerchant ships must remain at
sea, reducing their effectiveness and increasing their
vulnerability to other forms of attack. Without air
superiority in the areas to be mined, however, aircraft
and surface ships would be unable to lay and replenish
minefields effectively, and it would be inefficient to use
submarines for dense mine-laying because of their
small capacity,slow turnaround time, and insufficient
numbers.
The third form of interdiction?attacking merchant
ships at sea?probably would increase in importance
for the Soviets if the conventional phase were pro-
longed and if they had first neutralized the threat from
US carriers, amphibious task forces, and submarines.
1
They acknowledge that this method would require a
sustained effort by massed forces, principally attack
submarines.
In their analyses, the Soviets distinguish between the
interdiction of merchant shipping in the open ocean
and the interruption of an enemy's military resupply
effort in offshore waters adjacent to an area of active
combat operations. They regard the interruption of
NATO's close-in sea communications as an important
aspect of the Navy's traditional role of supporting the
ground forces. The operations involved would be
concentrated in specific areas for brief periods of time,
conducted mostly by combined air and surface forces,
and directed against shipping with military cargoes.
Their objective would be to isolate NATO troops on
the Continent. The Soviets believe that the interrup-
tion of NATO's in-area sea communications under
such conditions in a long war could make a direct
contribution to a Pact victory on land.
Open-ocean interdiction alone, in the opinion of most
Soviets who have written about the subject, could not
determine the outcome of a war. Authoritative Soviet
writers believe an open-ocean campaign should be
carried out mainly by attack submarines, with a
primary objective of causing the West to divert its
forces to extensive antisubmarine warfare (ASW)
operations far from the USSR. These authors believe
that it is easier to attack than to defend merchant ships
and hope that a few submarines committed to this task
would tie up a disproportionate share of NATO assets
by inducing NATO to scatter its naval forces over the
sea lanes,
Some Soviets also believe that interdiction could make
an important, though not decisive, contribution to the
Soviet war effort, should a war be protracted. In their
view, attacks on shipping could in time impose a strain
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on defending navies, erode enemy economies, and
reduce enemy resources for military operations in
distant areas. They believe that simply by operating in
the sea lanes, Soviet submarines could force NATO
shipping to adopt defensive measures (such as convoy-
ing, circuitous routing, and zigzag tactics) that would
reduce its efficiency.
Most Soviet military planners, however, do not expect
to have to fight a protracted war?the kind of war in
which attacks against shipping would be significant.
They believe or hope that the opening phases of war
with NATO would be brief and decisive, perhaps
culminating in a nuclear exchange?which, in any
case, would destroy the ports upon which shipping
depends. Holding this belief, they have relegated
attrition-based strategies like interdiction at sea to a
position of secondary importance. This view has
strongly influenced their operational plannin train-
ing, force structure, and submarine design.
Most Soviet naval forces evidently are assigned to the
wartime mission of controlling the seas near the
USSR. Their exercises and training generally take
place in the context of anticarrier or antisubmarine
operations. For the most part, their submarines are
designed for attacks on a limited number of high-value
naval targets?such as aircraft carriers?rather than a
large number of less valuable targets.
Competing Requirements Itir Submarines
The Soviets almos,t certainly do not have as many
submarines, particularly modern nuclear-powered tor-
pedo attack units (SSNs), as they deem necessary to
perform the naval tasks most prominent in their
operat?ional planning. They probably plan on concen-
trating large forces in areas?such as the Mediterra-
nean, Barents, and Norwegian Seas?where they feel
that Western SSBNs, carriers, and amphibious task
forces pose a threat to the USSR. These areas are far
from the likely NATO sea lanes in the North Atlantic.
We believe that the SovietsAould release only a few
torpedo attack submarines a raid NATO's sea com-
munications as long as they felt threatened by Western
naval forces.'
' Soviet capabilities for interrupting the resupply of NATO under
different levels of effort are discussed in the appendix.
The Soviets' sea control operations in the Norwegian
Sea and in the area of the Greenland?Iceland?United
Kingdom (G-I-UK) gap probably would tie up a large
part of their submarine force. They evidently regard
the Norwegian Sea as a favored launch zone for
Western naval strike forces, particularly aircraft
carriers. Their exercise activity suggests that they also
believe NATO might attempt amphibious landings on
or near the Kola Peninsula, which could cause them to
withhold some submarines in the Barents Sea.
In addition, the Soviets probably believe that NATO
would send large numbers of attack submarines to the
Norwegian Sea to threaten the D-class SSBNs patrol-
ling there and the Y-class SSBNs en route to and from
the North Atlantic. They probably believe that protec-
tion of these strategic submarines would be particu-
larly important during the conventional and the
limited nuclear phases of war, when these submarines
would have to remain passively on station awaiting the
transition to full nuclear war.
Soviet deployments would be affected by NATO's
opening moves. If the Soviets concluded that NATO
did not intend to send naval forces into or near the
Norwegian Sea, they probably would release larger
numbers of submarines for operations in the North
Atlantic.
In any event, the Soviets almost certainly would
conduct some sea denial operations south of the
G-I-UK gap. These operations would be directed
primarily against NATO fleets, however, and only
secondarily against merchant shipping, because the
Soviets believe that regardless of how a war may begin
the major wartime objectives of their general purpose
naval forces are to reduce Western nuclear capability
and to protect their own SSBNs. We do not know
exactly how the Soviets would apportion their forces
between these tasks, but it seems likely that the
requirements on their general purpose submarines to
attack Western naval units south of Iceland would be
demanding, even if none of them were committed to
operations against merchant ships.
2
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Capability of Soviet
Attack Submarines in the Atlantic Ocean
And Contiguous Seas
Because the Soviets' naval strike aircraft have limited
ranges and their surface ships are vulnerable when
operating out of Soviet-controlled waters, Soviet suc-
cess in sinking merchant ships at sea would depend
primarily on the availability and capability of the
general purpose submarine force for this task.
The USSR currently maintains in its western fleets an
active inventory of 173 attack submarines, most of
which are based in the Northern Fleet (see table 1). Of
this number, 126 are long-range units with enough
endurance to operate in the major shipping lanes.
Fifty-six of these long-range submarines are nuclear
powered and have almost unlimited range. The other
70 are long-range diesel submarines capable of operat-
ing more than 15 days on station within a 2,400-nm
radius. The remaining 47 submarines belong to the
obsolescent medium-range R- and W-classes, which
have an endurance of 20 days on station when
operating within 1,200 nm of their bases in the USSR.
To be effective against the major shipping lanes
between the United States and Europe, they would
require forward basing. After a war began, however,
any of them in the North and Mediterranean Seas or
the Atlantic Ocean would be unable to return to Soviet
submarine bases in the Baltic and Black Seas and
would have insufficient range toreturn to the Northern
Fleet for replenishment.
The focus of a Soviet campaign against Western
shipping would probably be the North Atlantic, and
the main threat would be the 112 long-range attack
submarines based in the Northern Fleet?the only
fleet in the western USSR that would have access to
the Atlantic sea lanes.
Because airlift could not meet the enormous logistic
requirements of fighting a modern war with conven-
tional weapons, NATO would have no choice but to
' Soviet Naval Aviation is poorly suited for interdicting most of the
Western sea lines of communication. Those aircraft that are
equipped with antiship missiles have relatively short combat radii,
which rule out their use over most of the major sea lanes in the North
Atlantic. They have some capability near the United Kingdom and
the Continent, but NATO's ground-based air defenses could make
. strikes there particularly hazardous.
3
-vepet,
use sealift to resupply its armies in Europe. Its long and
vulnerable shipping routes could theoretically be
severed at any point between the ports of embarkation
in the United States and the ports of destination in
Europe. Thus, the Northern Fleet submarine force
poses an obvious threat to NATO's use of the North
Atlantic in wartime.
On the other hand, the ability of that force to stem the
flow of NATO shipping would be constrained by th4
submarines' low operational availability and limited
torpedo capacity, the long transits they must make and
the lack of replenishment opportunities while out of
area, the turnaround time required between patrols,
combat attrition (especially as the submarines funnel
through geographic chokepoints to reach the sea
lanes), and problems with weapons effectiveness and
target acquisition.
Availability for Operations
The operational availability of Soviet attack subma-
rines is low, and this would reduce their usefulness for
interdiction. This limitation apparently stems primar-
ily from poor quality control and from inefficiencies in
the design, production, and maintenance of the subma-
rines. The Soviets also may have expanded their
nuclear submarine fleet faster than they have built
the facilities and trained the personnel for repairing
them
On the basis of long-term observation of the force and
other evidence, we judge that at any given time six out
of every 10 Soviet attack submarines would be avail-
able?with varying degrees of effectiveness?for com-
bat operations in distant waters. In wartime the Soviets
would have difficulty sustaining the initial level of
deployment, however, because of combat attrition and
because the increased use could lead to more of the
materiel failures that have characterized their peace-
time operations. In peacetime, only about 10 percent of
the Soviet submarine force is away from the USSR's
coastal areas at a time.
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Table 1
Fleet Distribution of Soviet Attack Submarines,
September 1978'
Range
Estimated
Torpedo
Loads
Northern
Fleet
Baltic
Fleet
Black Sea
Fleet
Cruise Missile Submarines
Nuclear-Powered (SSGN)
Class Missiles
C-I 8 SS-N-7
long
12
9
0
0
C-II 8 SS-N-9
long
12
3
0
0
E-II 8 SS-N-3/12
long
8
15
0
0
P 10 possibly SS-N-9
long
Unknown
1
0
0
Total SSGNs
28
Diesel-Electric (SSG)
Class Missiles
J 4 SS-N-3
long
6
12
0
0
W Long in 4 SS-N-3
medium
10
0
2
1
W twin cylinder 2 SS-N-3
medium
12
0
0
2
Total SSGs
12
2
3
Total Cruise Missile Submarines
40
2
3
Torpedo Attack Submarines
Nuclear-Powered (SSN)
A '
long
Unknown
2
0
0
E
long
8
0
0
0
N
long
20
8
0
0
V-1
long
16'
12
0
0
V-11
long
16'
6
0
0
Total SSNs
28
Diesel-Electric (SS)
long
22
36
5
0
long
6
0
0
0
medium
14
10
0
2
long
22
5
0
4
medium
12
5
15
10
Z
long
22
3
4
Pacific
Fleet
2
0
14
0
16
4
2
0
6
22
0
5
4
3
0
12
19
3
0
0
15
5
....... ?
Total Torpedo Attack Submarines
?
87
?
24
. ,
17
,..?
1 ->
-...
54
Total long-range attack submarines
112
9
5
59
Total medium-range attack submarines
15
17
15
17
Grand Total
127
26
20
76
' Numbers include submarines in repair and on sea trials, but not
auxiliary, radar picket, coastal and reserve units. Two SSNs (an N
and a V-I) have been inactive for many years and are here
considered to be in reserve.
I Torpedo estimates assume that Soviet submarines are loaded with
standard 2I-inch torpedoes. It is possible that submarines which lack
torpedo reloads, such as the J-class, could increase their loadings by
carrying two small weapons in place of a large one.
..'S"tuckt,
'The Soviets have built five A-class SSNs. Of these one has been
dismantled, two are fitting out, and tworya submarines. 'V-class submarines probably also car rocket-assisted
nuclear depth bombs for use against other
4
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Torpedo Reloads
Another factor limiting the usefulness of many Soviet
attack submarines for interdiction would be their
apparently small capacity for carrying torpedoes. The
cruise missile submarines evidently carry few or none
beyond those already in the tubes. Thus, these subma-
rines (the C-, E-II-, and J-classes, which together form
nearly one-third of the USSR's fleet of long-range
attack submarines) would be ill equipped for interdic-
don as a secondary task, We assume they would not
use their missiles against merchant shipping. The long-
range torpedo attack submarines, which are more
likely to be committed to interdiction, have greater
capacity (from 16 to 22 torpedoes each); but they are
multipurpose submarines that ordinarily carry a vari-
ety of torpedoes, some of which are nuclear or for
ASW and robably would not be used against cargo
ships.
These weapon loads are consistent with a naval
strategy that stresses the likelihood of a short, nuclear
war and the primary importance of destroying a small
number of high-value enemy naval ships. The rela-
tively small torpedo loads would seriously constrain an
effort to interrupt the resupply of NATO, however,
because the interdiction of merchant shipping requires
a large number of torpedoes.
Although they do not carry many torpedoes, the
submarines generally have a high salvo capability:
nearly all Soviet attack submarines have six forward
torpedo tubes (most US nuclear-powered attack sub-
marines have four).
Another indication that the Soviets are not concentrat-
ing on preparations for a long conventional war of
attrition at sea is the composition of the torpedo loads.
Recent evidence indicates that Soviet submarines may
carry a fairly high ratio of nuclear to conventional
weapons. In a conventional war, the salvo capability
and the Soviets' preference for massing their forces
against important targets like aircraft carriers would
tend to offset the effect of the small weapons loads. The
need for mass attack, however, would leave fewer
submarines available fo. other tasks
5
SteFeL
Time on Station
Several factors seriously limit the amount of time
Soviet submarines could spend on station in the North
Atlantic. These include the long transits they must
make to reach operational waters, the lack of re-
plenishment opportunities in those waters, and the
need for time in port between patrols
Long Transits. Soviet submarines would have to travel
long distances to reach interdiction points on likely
NATO shipping routes. Western shipping could tie
routed southward toward an area west of Spain, where
one route could lead toward the Continent and
southern England and another could enter the Medi-
terranean (see figure 1)'. We assume that the Soviets
would give increased priority to interdiction if the
conventional phase of a NATO-Pact war were pro-
longed and NATO succeeded in stopping the Pact's
advance on the central front. In such a situation,
NATO merchant ships could sail for many different
ports, and the value to the Pact of any particular
chokepoint near the Continent would be reduced. In
addition, NATO's ASW capabilities probably would
be greater near shore. Thus, the same circumstances
that would make interdiction valuable to the Soviets
could also force them to concentrate their interdiction
forces farther out at sea and farther from the USSR.
Lack of Replenishment Opportunities. The Soviets
would have to return their submarines to home waters
to rearm them. They acknowledge in their writings
that the maintenance of distant submarine operations
requires logistic support dispersed over a wide area.
Submarine tenders and missile support ships could
transfer torpedoes at open anchorages and cruise
missiles at sheltered anchorages or in port. If they left
Soviet-controlled waters in wartime, however, these
resupply ships would be vulnerable to attack, and the
Soviets probably would not count on them for re-
plenishment. Any Soviet merchant ships at sea when
war began would probably soon be sunk or captured
and would not be available to support Soviet submarine
operations in the North Atlantic
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Submarine Transit Distances to Possible Wartime Sea Lane
Figure 1
Svalbard
. (Nor.)
Greenland
(Dem)
Northern Fleet
submarine
bases
end
Turnaround Time. Submarines have to spend some
time in port between patrols, and in a long campaign
thdy need additional time for major repairs. In World
War II, US and German submarines required some 25
days' turnaround time and required extensive repairs
after seven or eight combat patrols
Our observation of the Soviets' maintenance pro-
cedures suggests that they are unlikely to improve
much on the World War II time for the turnaround of
diesel submarines. They probably could not turn
around a nuclear submarine after a patrol in signifi-
cantly less time than the US Navy requires for its
SSENs?currently 32 days. A rough measure of
efficiency is that the Soviet Navy requires some three
eece,t,
NE Possible sea lane
20/48 Travel time for round trip
in days (nuclear/diesel)
years to overhaul and refuel a nuclear-powered subma-
rine?more than twice as long as the US Navy.
Combat Attrition
This need to return to base for replenishment and
refurbishment means repeated passage through such
chokepoints as the G-I-UK gap, where the Soviet
submarines would be especially vulnerable. Even on
station, they would be continuously within range of
NATO's land-based ASW aircraft, as well as other
ASW platforms.
Weapons Effectiveness
The World War II history of US and German antiship
attacks indicates that the number of torpedoes fired
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was much greater than the number of ships sunk.
Although Soviet torpedoes appear to be technically
reliable (about 85 percent), reliability is only one of
several factors in the effectiveness of torpedo attacks,
and other factors would tend to reduce that effective-
ness. For example, we judge from some Soviet writings
that the Soviets plan on firing their torpedoes from
long ranges?a practice that would substantially
reduce accuracy.
In Western navies, a single nonhoming torpedo has an
even chance of hitting a straight-running surface ship
at short range (2,000 yards or less). The odds against
hitting a fast-moving, maneuvering target are longer.
Accordingly, we estimate the Soviet hit rate in
wartime at no better than about 25 percent for each
torpedo fired (the 0.85 system reliability multiplied b
an optimistic 0.30 probability of hitting the target).
The presence or absence of escorts among the mer-
chant ships is another factor that would affect the
Soviet weapons effectiveness against shipping. Soviet
writings indicate that to reduce exposure to escorts
Soviet submarines would use tactics that are likely to
increase the ranges at which they would launch their
torpedoes?and thus reduce their effectiveness. If they
were diverted into firing some of their torpedoes
against the escorts?fast, maneuverable, shallow-draft
ships that would be difficult targets?they would have
still fewer left to use against shipping.
Target Acquisition
In wartime, the Soviets probably would activate agents
in North America to collect and communicate intelli-
gence on shipments of war materiel to Europe. They
probably would also launch ocean reconnaissance
satellites to track the ships as they moved eastward.
Soviet ELINT-gathering ocean reconnaissance sat-
ellites (EoasATs) and radar ocean reconnaissance
satellites (aoRsAis), used in concert, can effectively
collect intelligence against emitting US warships
under normal operating conditions because the two
space systems complement each other and because US
naval ships of similar types carry similar radar suites.
Both systems are vulnerable to countermeasures,
however, and indicate that
the RORSAT is not yet fully operational
3t.ege,L
But even if the reconnaissance satellites worked well
and the merchant ships continued to use their radars
and radios, the Soviets almost certainly could not
convert dockside or satellite-derived intelligence into
targeting data adequate for submarine commanders to
locate and attack specific merchant ships at sea. The
data yielded would be too crude to enable the Soviet
submariners to select the specific ships with military
cargoes.\
Furthermore, Soviet
torpedo attack submarines (the strike forces most
likely to be used against shipping) could receive
satellite-derived target data only indirectly?primarily
via the submarine broadcast from Moscow?and
probably several hours after the satellite had passed
over the target.
If the Western merchant ships practiced electronic
emissions control, RORSAT would become the Soviets'
primary satellite-borne ocean surveillance platform
and simultaneously would become less effective be-
cause of losing the external tipoff data on which it is
highly dependent for targeting. Even under optimum
conditions (including receipt of tipoff information), a
pair of RORSATS could detect a large surface ship in the
aircraft carrier transit lanes of the North Atlantic only
once a day, on the average, and during that time a fast
merchant ship can travel some 500 nm.3
NATO logistic managers could reduce the value of a
single ship by dispersing critical cargoes among many
ships. They could complicate targeting by convoying
ships loaded with economic goods together with ships
carrying military cargoes. Alternatively, they could
concentrate military cargoes in fast ships that would
sail independently, at least in the open-water phase of
their trips. The speed of these ships would sharply
reduce the effectiveness of Soviet diesel submarines
except at the terminal points of the voyage.
' This conclusion is based on a computer simulation\
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NATO Sealift Resources
NATO is an alliance of maritime nations and has an
extensive inventory of merchant ships.' Moreover, the
construction of merchant ships?and thus the potential
replenishment of the inventory?is high: Lloyd's
Register of Shipping reported that in 1976 over 1,000
merchant ships, totaling nearly 30 million tons, were
constructed in the Free World. This was down 4
million tons from the 1975 peak, and we expect further
reductions as a result of overbuilding in the early
1970s, economic recession, and decreasing demand for
new tankers. These figures nonetheless indicate consid-
erable capability to replace losses in shipping even
early in a conventional war.
US planning for the military resupply of NATO in a
conventional war assumes a large amount of military
support shipping that increases steadily during the
war. Three or four hundred ships?or even more?
could be en route to Europe within the first 30 days of
hostilities, and during the next 30 days some 500 more
could depart. More than 1,000 additional ships could
sail later, making a total of 2,000 sailing with military
cargoes in the first 90 to 120 days of war. Economic
and military shipments together might total some
3,000 a month.' (c)
' There is disagreement within the US Government on how many
ships would be available for sealift if necessary, but NATO clearly
has more merchant ships than it is likely to need. According to
Lloyd's, in 1976 there were over 9,000 NATO-flag merchant shins
of over 1 000 sross resister tons. A recent studY
oncluded that over 5,000 of these would
be suitable for sealift of supplies and materiel to Europe.
Additional Western-owned merchant ships flying Panamanian and
Liberian flags of convenience also probably would be available for
11,500 merchant ships coitumd for the resupply of NATO. The
sealift if needed. An olde study estimated that about
numlier used in this study-5,832?comes from Lloyd's but
excludes ships of less than 6,000 gross register tons. This number is
close to the estimate by the Naval Intelligence Support Center
(NISC) on the size of the NATO-flag merchant fleet. NISC data
show 5,565 NATO-owned merchant ships larger than 6,000 GRT.
These figures understate the tonnage available, NISC believes,
because the 6,000 GRT cutoff excludes many ships?especially
those with a roll-on/roll-off capability?that could conduct trans-
oceanic operations. If these ships and US-controlled foreign-fla
ships were added to the NISC total, it would become 6,208.
Losses of military equipment probably would be more
important than losses of ships, which probably could be
replaced on a one-for-one basis during the war. To
reduce appreciably (by, say, 25 percent) the number of
military cargoes delivered to Europe, the Soviets would
have to identify the ships carrying those cargoes and
then maintain large strike forces in the sea lanes. If
economic shipping dwindled during the war, Soviet
efficiency in sinking military cargoes could increase.
The appendix contains an analysis of Soviet capa-
bilities, using a computer simulation of a modern
interdiction campaign in the Nbrth Atlantic and
assuming long-range attack submarines in the North-
ern Fleet as strike forces. It addresses the effects of the
above constraints, with various force levels, on the
capability of the submarine force to interdict shipping.
It shows that, regardless of the level of commitment,
Soviet forces have little capability to disrupt the
resupply of NATO by sinking merchant ships at sea.
Outlook
Contemporary Soviet writings, exercises, and naval
force trends indicate that for the next decade or so
there are unlikely to be any militarily significant
increases either in Soviet willingness to allocate forces
to interdiction or in the interdiction capabilities of the
forces themselves. This judgment assumes that:
? The West continues to maintain and deploy strong
offensive naval forces capable of attacking targets in
the USSR with nuclear weapons?a threat that causes
the Soviets to commit strong forces of their own in
counteraction.
? NATO maintains strong air defenses which could
and probably would deny Soviet aircraft free access to
the sea lanes in wartime.
8
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A key element in deterring the Soviets from fully
exploiting Western dependence on long sea lines of
communication in wartime is the credibility of the
NATO carrier and SSBN threats to the USSR. The
specter of NATO carrier task groups in or near such
areas as the Norwegian Sea and the eastern Mediter-
ranean, for example, would almost certainly hold large
Soviet forces in those areas?and well away from the
major sea lanes. Even if the NATO carriers were more
distant (in the North Atlantic west of the United
Kingdom, for example), the Soviets probably would
still regard them as a threat and keep a sizable
submarine force available to counter them. Soviet
submarines engaged in interdiction operations prob-
ably would be in waters farther south and could not be
recalled to the Norwegian Sea in time to prevent
Western carrier strike forces from penetrating into the
Norwegian Sea and launching raids on Northern Fleet
naval bases and other targets in the northwestern
USSR.
If, on the other hand, the West stationed high-value
targets like carriers on the major shipping routes,
Soviet naval strike forces might be attracted to those
targets and thus be in a position to threaten Western
shipping as well.
To some extent, Soviet naval mission priorities are
scenario driven. Thus, any reallocation of naval forces
would depend on the outcome of the initial battles, at
sea and on land. If NATO checked the Pact advance in
Central Europe and the war became prolonged, Soviet
interest in interdiction probably would increase, be-
cause cutting the sea lanes?particularly in waters
adjacent to a theater of military operations?could
then affect the outcome of the war. This would be
particularly true if attrition or Western strategy
reduced the carrier threat to the USSR, enabling the
Soviets to free more forces to attack merchant ships.
9
'tfrer<
If the war in Europe were stalemated and Western
strike forces remained largely intact, however, the
Soviets would face a hard choice: to try to interrupt the
resupply of NATO or to concentrate their remaining
naval forces against SSBNs and carriers. The Soviet
tendency to assign higher priority to military targets
suggests that under these circumstances they would
continue their concentration against NATO's offen-
sive naval forces. Should they elect to send most of
their surviving attack submarines against merchant
ships, they would leave Western naval strike and
intervention forces free to attack important Pact
ground and naval targets.
?
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?
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Appendix
Analysis of Soviet
Interdiction Capabilities
The analysis described in this appendix examines
Soviet submarine capabilities against Western ship-
ping in the North Atlantic. Using a computer-based
model for convenience, it considers the ability of Soviet
submarines to deliver torpedoes against US convoys to
Europhe analysis focuses on three scenarios, which
postulate different Soviet commitments of attack
submarines to interdiction. The first shows the effort
we would expect the Soviets to make (giving priority to
antifleet operations); the second scenario assumes
roughly equal emphasis on antifleet and antishipping
operations; and the third shows the Soviets using all
their available long-range submarines against NATO
shipping.
Assumptions used in our base study tend to "worst
case" the situation for NATO and result in optimistic
exchange ratios for the USSR. Key assumptions are:
? Submarines spend 15 days on station.
? Each submarine fires all its torpedoes (except two
withheld for self-defense) against merchant ships in a
target-rich environment; that is, each finds as many
targets in 15 days as it has torpedoes.
? Turnaround time between patrols is 25 days (vari-
ations of the basic model were run with 15-day
turnaround periods).
? Submarines suffer 20-percent attrition per patrol
during transit and no attrition on station.
? Shipping travels a southern route. Submarines inter-
dict merchant ships primarily in two areas?west of
the Azores and west of the Bay of Biscay,
'The model, Which is called Firearm and is unclassified, was
developed by Science Applications, Incorporated, of Englewood,
Colorado. it is described in a "User's Manual," SAI-77-143-DEN,
dated 26 August 1977. Copies of the manual can be obtained from
SAI
11
? The Soviets schedule their departures so as to
maintain an almost continuous submarine presence in
the shipping lanes.
? Soviet Northern Fleet bases are undamaged and
continue to support submarine operations. 4
? The Soviets achieve a hit rate of about 25 percent for
each torpedo fired (0.85 technical reliability multiplied
by 0.3 for accuracy).
? A single hit sinks or disables a merchant ship.
? NATO air superiority prevents the Soviets from
replenishing submarines from non-Warsaw Pact terri-
tory and forces the submarines to return to home
waters for replenishment. (In an alternative World
War II-like scenario, we simulated Soviet submarine
deployments out of bases in France and southern
Norway, which we assumed to have come under Pact
control. From these forward bases, and targeted
against shipping at points north and south of Ireland,
Soviet submarines increase NATO ship losses by some
50 percent.)
? Torpedoes with nuclear warheads and cruise missiles
are reserved for military targets; none are expended
against merchant ships.
? Nuclear-powered submarines transit at speeds of
advance (SOAs) of 12 knots, diesels at 5. (These
approximate the speeds used by the Soviets and
presume some minimal concern for NATO ASW
capabilities during transit. We ran a variation of the
model using SOAs of 15 and 8 knots, but they did not
change the results significantly.)
? The Soviets know the general location of Western
merchant ships (notwithstanding the difficulty of
using space systems for targeting) but cannot specifi-
cally identify military shipping because economic
shipping continues.
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Table 2
NATO Losses in a 120-Day Interdiction Campaign:
Three Scenarios
Scenario Level of Soviet
Effort Assigned
to Interdiction
Soviet Submarines
Participating in
Interdiction Campaign
The "anticipated level":
20% of available long-range
torpedo attack submarines
5 F/T/Z-class SSs 4
2 N-class SSNs
2
Intermediate level: all avail-
able long-range torpedo
attack submarines except
V-class
17 F/T/Z-class SSs
5 N-class SSNs
3
Maximum level: all avail-
able long-range torpedo
attack and cruise missile
submarines
7 C-class SSGNs
9 E-II-class SSGNs
.I-class SSGs
SN-class SSNs
12 V-class SSNs
27 F/T/Z-class SSs
Total
Western
Ships Sunk
or Disabled'
Losses as a
Percentage of
Total NATO-Flag
Ships (rounded)
Losses as a
Percentage of Total
Military and
Economic Cargoes
Shipped (rounded) '
38
0.7
0.3-0.5
115
2.0
1.0-1.4
277
4.7
2.3-3.5
' These numbers assume a Soviet hit probability of about 25 percent
and that a single hit disables a target.
'Our calculations included only NATO-flag ships of 6,000 gross
register tons or more. They excluded more than 3,000 comparable
Liberian- and Panamanian-flag ships, some of which probably also
would be used for sealift if needed.
This assumes monthly sailings of 2,000 to 3,000 ships carrying
military and economic cargoes.
4 F-class submarines deployed to the Mediterranean are excluded
from the strike forces in Scenarios 1 and 2.
Table 2 summarizes the results of the three levels of
effort, all using these assumptions.
Scenario 1 (Anticipated Level of Effort)
This scenario assumes that the Soviets' main reason for
attacking merchant ships in the open ocean is to create
a diversion that will cause NATO to spread its forces
over the sea lanes. This scenario represents the level of
Soviet effort that we would consider likely in the early
phases of a war, while Western SSBNs, aircraft
'bious task forces posed a threat to
carriers, and a
the USSR
In this scenario, under favorable conditions the subma-
rines could sink or disable some 38 ships within 120
days. This number is less than 1 percent of the total
ships available to NATO (see section on NATO sealift
The Northern Fleet normally supplies about 10 attack submarines
for the Soviet Mediterranean Squadron. Although it is unlikely, we
assume for purposes of Scenario 3 that these forces would be
available for operations against merchant ships in the North
Atlantic.
resources) and less than 1 percent of the combined
military and economic cargoes shi ped from the
United States during that period.'
Scenario 2 (All Available Long-Range Torpedo Attack
Submarines Except V-Class)
This scenario assumes that the conventional phase of
war in Europe continues and the Soviet leaders risk
sending all available long-range torpedo attack subma-
rines in the Northern Fleet against merchant ships,
with the exception of the 10 or so available V-class
SSNs, which would be employed mainly in offensive
and defensive ASW operations. The emphasis ac-
corded interdiction would be approximately the same
as that devoted to countering Western SSBNs, aircraft
carriers, and amphibious task forces
'Figure 2 shows the effect on ship losses of varying the number of
submarines committed to interdiction in the three scenarios
12
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Cumulative Western Ship Losses
Ships
Figure 2
350
300
250
200
Scenario 3
(staggered deployment)
150
100
50
12 24 36
Days
48 60
72 84 96
08 120
Under favorable operating circumstances, this larger
number of submarines could destroy or disable more
than 100 merchant ships, constituting about 2 percent
of the NATO-flag ships and 1.0 to 1.4 percent of the
military and economic cargoes shipped.
Scenario 3 (Maximum Effort)
This scenario assumes that all available long-range
torpedo attack and cruise missile submarines in the
Northern Fleet and Mediterranean Squadron are sent
against merchant ships in the North Atlantic, leaving
no submarines to combat Western naval forces. This
force could sink some 277 merchant ships, a level of
attrition that would represent about 5 percent of
NATO-flag ships of 6,000 gross register tons or
greater and about 3 percent of cargoes shipped during
13
a 120-day period. Our analysis assumes that the
Soviets stagger their submarine departures in order to
maintain an approximately continuous presence in the
sea lanes.
We have assumed that the C-, E-II-, and J-class
submarines would use only their torpedoes, not their
cruise missiles, against shipping. If we assumed that
they had conventional warheads on half their cruise
missiles and used them against merchant shipping, the
number of Soviet weapons available for interdiction
would increase by about 100. We have not made this
assumption in our calculations of losses in Scenario 3;
we have, however, weighted our calculations in the
submarines' favor by assuming a higher proportion of
' Figure 3 shows the effect of attrition in Scenario 3 by comparing
cargoes destroyed with cargoes delivered
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Cargoes Delivered and Cargoes Lost in a Hypothetical All-Out Interdiction Campaigni
Cargoes
Figure 3
12,000
10,000
8,000
6,000
4,000
2,000
Cargoes destroyed in Scenario 3
12 24 36 48 60 72 84 96 108 120
Days
1. The cargoes are both military and economic.
2. Data on cargoes delivered reflect uncertainties regarding the number of
economic shipments that would take place.
Nc.<
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antiship torpedoes (vs. ASW torpedoes) than the
evidence would indicate. "Alert" submarines in peace-
time evidently carry mixed weapon loads, including
ASW and nuclear torpedoes. If they continued this
loading pattern in wartime?as seems likely?they
would have fewer torpedoes than we have postulated
for them to expend_acainst merchant ships and would
sink fewer ships.
Other Considerations
Other, more realistic, operating conditions likely to
prevail in wartime probably would make ship losses
lower than those attained in the three scenarios of this
analysis. Some hits, for example, might not disable or
sink a ship?but we have assumed that they all would.
If NATO economic shipping continued, Soviet at-
tempts to identify the ships carrying military cargoes
could force the Soviet submarines to spend more time
on station searching for targets (beyond the 15 days
assumed in the model). This would increase their
vulnrahiIty and reduce the number of patrols over
time.
Realistically, submarines would be subject to attrition
during their entire patrols, not merely during transits.
If submarine attrition were 0.3 to 0.5 per patrol
(instead of 0.2 as assumed in this analysis), Soviet
ability to sustain an at-sea interdiction campaign
would be sharply reduced
All of the scenarios we examined were constructed to
the Soviets' advantage. If as an upper bound we
assumed a torpedo hit rate which their submarines
could achieve if all their attacks were made at short
range against slow-moving, straight-running, unde-
fended ships (about 0.5 accuracy), NATO losses in
Scenario 3 would increase to about 11 percent of
NATO-flag shipping and 6 to 8 percent of the cargoes
shipped.
15
On the basis of the analysis, we consider it unlikely
that the Soviets, even with a maximum effort, could
destroy as much as 5 percent of NATO military and
economic cargoes during the first 120 days of war by
attacking merchant ships at sea.
Sensitivity Cheeks
Numerous variations of the basic model were run to
check its sensitivity to changes in its basic assumptions.
Table 3 summarizes the results obtained
Rather than "pulsing" their submarines to maintain a
nearly continuous presence in the shipping lanes, the
Soviets could "surge" all those available when a war
began.' Over time, surge deployment would sink about
the same number of Western ships as staggered
deployments, but it would leave periods when no
submarines were operating in the sea lanes, leaving the
North Atlantic safe for shipping (these periods show as
plateaus in figure 2). In a 120-day campaign, surging
Soviet submarines in Scenario 3 would increase
NATO losses by about 15 percent(roughly 2.7 to 4
percent of the cargoes shipped)
Other variations include reducing the submarines'
turnaround time and concentrating their attacks in
the vicinity of the Bay of Biscay. Even with the
most favorable combination of these variations, the
model indicated a resulting loss of no higher than 6
percent of the NATO ships, or 4.3 percent of the
cargoes shipped.
Another alternative--predeploying all available submarines?
could result temporarily in higher NATO casualties because it
would eliminate wartime attrition on the submarines' first outbound
trip and could increase time on station. We do not consider such an
action likely, however, because in the Soviet iiewit probably would
precipitate an unacceptable NATO response
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Table 3
NATO Losses in a 120-Day Interdiction Campaign:
Variations on the Basic Model
Scenario 1
Scenario 2
Scenario 3
Total
Ship
Losses
Percentage of
Total NATO
Total
Ship
Losses
Percentage of
Total NATO
Total
Ship
Losses
,
Percentage of
Total NATO
Ships
Cargoes '
Ships
Cargoes '
Ships
Cargoes '
Base Case 2
38
0.7
.3-.5
115
2.0
1.0-1.4
277
4.7
2.3-3.5
Base Case Variations
15-day turnaround time
44
0.8
.4-.6
133
2.3
1.1-1.7
303
5.1
2.5-3.7
Attacks concentrated in
Bay of Biscay area
40
0.7
.3-.5
122
2.1
1.0-1.5
280 ,
4.8
2.3-3.5
Biscay contact area plus
15-day turnaround
45
0.8
.4-.6
136
2.3
1.1-1.7
310
5.3
2.6-3.9
Attacks concentrated west
of the Azores
36
0.6
.3-.5
109
1.8
.9-1.3
259
4.4
2.1-3.2
Azores contact area plus
15-day turnaround
40
0.7
.3-.5
121
2.0
1-1.5
283
4.8
2.3-3.5
Surge deployment
54
0.9
.5-.7
170
2.9
1.4-2.1
318
5.5
2.7-4.0
Surge deployment plus
15-day turnaround
60
1.0
.5-.8
188
3.2
1.6-2.3
341
5.8
2.8-4.3
Surge deployment plus
Biscay contact area
57
1.0
.5-.7
179
3.0
1.5-2.2
318
5.4
2.6-3.9
Surge deployment plus
Azores contact area
49
0.8
.4-.6
153
2.6
1.3-1.9
288
4.9
2.4-3.6
Surge deployment plus
15-day turnaround plus
Biscay contact area
62
1.1
.5-.8
192
3.3
1.6-2.4
350
6.0
2.9-4.3
Surge deployment plus
15-day turnaround plus
Azores contact area
60
1.0
.5-.8
188
3.2
1.6-2.3
341
5.8
2.8-4.2
' Cargo data reflect uncertainty as to the number of ships with
economic cargoes that would sail for Europe. We assumed here that
2,000 to 3,000 ships with both military and economic cargoes sail
each month.
' The basic assumptions are listed at the beginning of this appendix.
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