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German Submarine Research And Development During The Inter-War Years
AUTHOR Major Edward N. Rohloff, USAF
CSC 1989
                        EXECUTIVE SUMMARY
    As World War I drew to a close, Germany was left
defenseless.  The Treaty of Versailles prohibited the German
people from maintaining virtually any type of military forces.
Germany's U-Boat forces were completely dissolved.  Only a token
number of antiquated surface vessels were allowed in operation.
    The post war years brought great attention to the submarine
from the military forces of the day.  Submarines had played an
important role in the First World War.  In the years after the
war, international concern was levied in the interest of
maintaining military parity of the world powers.  The victors of
the war strived to achieve this equality through conferences
dealing with arms limitations.  Germany was ignored at these
talks because of her status as a result of the treaty.
    Germany, however, began clandestine activities in an attempt
to retain some of the technology which she had garnered during
World War II.  In due time Germany had not only managed to
continue research and development but had also actually trained
some crew members in the U-Boat business.
    When Adolph Hitler came to power, Germany had only to reveal
her secret and she was back in the business of being a viable
sea power.  This complete evolution allowed Germany to quickly
build her forces in preparation for the aggression which she was
about to display on the rest of the world.  Had it not been for
the resistance of a few key players in this building process,
Germany may have been much stronger at the onset of
hostilities.  Her U-Boat forces may very well have led her to
much greater heights.
               German Submarine Research and Development
                       During the Inter-War Years
Through relentless clandestine operations Germany would retain
and actually improve her U-Boat technology base despite the
restrictions of the Treaty of Versailles.
I.  Post World War I Awareness
    A.   International attention of submarine warfare
    B.   Attempts to regulate naval forces
II. German Research and Development of U-Boats
    A.   Clandestine Operations
    B.   Actual production
III. Establishment of the Naval U-Boat Arm
    A.   Tactics development
    B.   Force Structure
          German Submarine Research and Development
                 During the Inter-War Years
    The First World War demonstrated to the world that
submarine forces could be an essential ingredient to any
country's naval and overall warfighting capability.  German
U-Boats wreaked havoc on Allied surface ships throughout the
war.  Hundreds of thousands of tons of shipping were sent to
the depths of the seas as a result of this born again weapon
system.1 Submarines had been in use for decades, but never
before had they been used with such devastating results.
Germany's use of submarines during this period overshadowed
any other country's attempts at submarine warfare to date.
Germany would demonstrate during World War II how the U-Boat
had become an integral element of her blitzkrieging war
    With the end of World War I, the Treaty of Versailles
forbade Germany of possessing any U-Boats and dictated that
the Imperial Navy be reduced to only a handful of very old
surface ships.2 Germany however would not forget the
importance of the U-Boat as an essential element of military
might.  Through relentless clandestine operations Germany
would retain and actually improve her U-Boat technology base
despite the restrictions of the Treaty of Versailles.
    The inter-war years between 1918 and the early 1930 `s
produced international concern and attention toward submarine
warfare.  The world remembered the successful campaigns of
the German U-Boat fleet during World War I.  Some recalled
the thousands of lives lost and the perils of those left
stranded in life boats after submarine attacks.  For others,
the submarine was an instrument of power and a must for any
viable military force.  A conference in Washington D.C., in
October of 1921, attended by representatives of the United
States, Great Britain, France, Italy, and Japan addressed the
topic of limitations on naval armaments. 3 The size and
operations of submarine forces were barely mentioned.  Great
Britain wanted to abolish their use altogether, but the other
conference members disagreed.  Again in 1930 the
aforementioned countries sent representatives to confer over
naval issues.  This conference took place in London. 4 The
result of this debate was a lame international policy,
embodied in the London Protocol of 1934, which
established a set of rules for submarine warfare:
         1. The submarine must surface before
         2. Crews and passengers had to be guaranteed
            safety.  They could not be abandoned in
            small boats on the high sea.  Either they
            had to be taken aboard the submarine
            (which was impossible in terms of space),
            or the submarine captain had to hail a
            neutral ship to take them aboard (most
            improbable), or the ship had to be let
         3. Merchant ships were not to be armed.
         4. Merchant ships were not to use radios to
            call for help or warn other ships at sea
            about the submarine.5
Obviously the rules of the London Protocol would not stand up
during hostilities.
    World powers at this time between the great wars acted as
if they had blinders on where Germany was concerned.  The
Treaty of Versailles had forbidden any build up of German
military forces.  As a result of this, England, Japan,
France, Italy, and the United States failed to pay heed to
Germany's technological advancements in U-Boat construction
during these years.  The so called world powers did not
invite Germany to the international meetings designed to
regulate the naval forces of these countries.
    Germany, however, had other ideas.  At the close of World
War I, Germany was concerned about national defense and the
limitations of the Treaty of Versailles.  How could she be
expected to dissolve her navy and leave her coastlines
undefended?  Despite efforts to retain some of her military
might for national defense, Germany was directed to dissolve
the U-Boat Inspectorate and the U-Boat Office.6
    Constrictions imposed on Germany by the treaty led to
clandestine activities masterminded by the great armorer of
Germany, Gustov Von Krupp.7 The Krupp family with its
international connections already had the framework to
continue the work of the U-Boat engineers and architects.  In
1922 Krupp dispatched the first of 40 German engineers to a
Dutch company at the Hague where they found employment
drafting U-Boat blueprints.8 Krupp managed this business
venture to respectability by selling shares in this new
company and also by sending submarine blueprints to Japan,
Spain, Turkey, Finland, and Holland.9 Before long, a
perfectly respectable international business had become a
breeding ground and training environment for Germany's ever
growing U-Boat engineering and design capability.
    Two U-Boats were built for the private account of that
Dutch firm - a 250 tonner at Abo in Finland, which was later
delivered to the Finnish Navy, and a 500 ton boat built in
Cadiz, which the Turks took over.  German engineers, dockyard
experts, and naval officers helped to supervise the submarine
construction.  Small groups of men - never more than
half-a-dozen at a time - travelled incognito to Spain and
Finland.  Naval officers of the executive and the engineering
branches, and naval contractors, posing as businessmen,
students, fitters, or employees of the Dutch company, went
there to relearn the problems of U-Boat handling.10
    Orders for submarines were received from around the
world.  The next logical step took place.  German engineers
well schooled in the design of the U-Boat soon became experts
in construction.  Lessons learned from World War I
construction were applied and a much more efficient and
capable class of boats emerged.  Germany was again cornering
the market in U-Boat design and construction despite the
restrictions imposed on her after the war.
    The next step toward rebuilding the U-Boat arm of the
navy was to covertly train sufficient numbers of crewmen in
U-Boat operations.  This was done by the establishment of the
Anti-submarine Warfare School at Kiel.  What appeared on the
surface as a center for a dozen officers and about sixty
enlisted men as training in navigation and naval art and
science indeed was the beginning of the new U-Boat force.
The men trained in civilian clothes in a very low key
environment.  Practical application and actual operations
took place in Finland.11
    Adolph Hitler had at this time been appointed Chancellor
of the German Republic.  The German Navy began manufacturing
U-Boat parts in secret.  Up until this time Germans had not
been involved in actual U-Boat production on native soil.  A
whole series of mysterious, heavily guarded sheds had sprung
up inside the Deutsche Werke and Germania shipyards in
Kiel.12 The Germans were building submarines, quite
illegally under the terms of the Treaty of Versailles.  The
year was 1934.  U-Boats of the type already designed,
constructed, and operationally tested by German engineers and
crewmen in Spain and Finland were laid to construction.13
Germany's naval rebuilding program was in full swing.
    On March 16, 1935, Adolph Hitler publicly repudiated the
Treaty of Versailles.  Germany would no longer conceal
escalation and rebuilding efforts of her naval forces.  The
rest of the world was forced to recognize the emergence once
again of the German people as a growing world power.  Three
months later Germany and Great Britain concluded the
Anglo-German Naval Agreement.  Under its terms Germany would
restrict the strength and size of her Navy to 35 percent of
that of the British Navy with exceptions to the size of the
German submarine forces.14
    The rest of the world stood by and watched Germany
rebuild.  Adolph Hitler was in full control and appeared to
be acting within the terms of international agreements.
England's hands were tied as a result of the Anglo-German
Naval Agreement.  The shroud which had hidden Germany's
secret, the illegal building operations, was dropped.  By mid
1935, U-1 the first U-Boat of the modern class was brought
out, ready to launch.  She began her first patrol just forty
two days after the signing of the new Naval Agreement.15
The stage was set for the ensuing buildup of the U-Boat arm
of the German Navy.
    Karl Doenitz was selected by the German High Command to
take charge of the new U-Boat arm.  Doenitz was a World War I
U-Boat commander who was captured by the British and spent
several months in a British prisoner-of-war camp.  Doenitz
feigned insanity and was released by the British for
repatriation to Germany.16 Doenitz' inter-war years were
spent in the German Navy on surface duty.  With his
appointment to head the U-Boat arm, Doenitz began to
conceptualize employment of the submarine force.
Commander Doenitz recalled his experiences countering
British convoys during World War I.  He was convinced that a
hunter killer tactic with individual submarines engaging
surface ships would not be the most effective utilization of
his submarine forces in the next war.  He devised the
Rudeltaktik (the wolf-pack strategy) in 1935.17 He felt
that convoys with their protective escort must be attacked
with "packs" of U-Boats as opposed to individual sorties on
search and destroy missions.
    Doenitz' concept of employment was that a single U-Boat
would operate on patrol to locate a convoy.  Upon sighting a
convoy, the U-Boat would disengage the intercept while
maintaining contact with the convoy.  The pack would then be
called in to converge on the prey.  The wolf-pack would
mostly engage on the surface to take advantage of their speed
and maneuverability.18
    Doenitz believed that an efficient U-Boat force would
have to number approximately 300 boats.  He envisioned 100
U-Boats at any one time on station in the North Atlantic.
Another 100 boats would be in port in routine maintenance and
resupply.  The remaining 100 boats would be enroute to and
from the patrol areas.  This force, he believed would be of
sufficient strength to starve Britain to death.19 Doenitz
had a difficult time convincing the power structure in
Germany of the need for such a large force.
    Eventually Doenitz was able to convince Hitler and
Admiral Raeder, the Commander in Chief of the German Navy, of
the importance of increasing the size of the U-Boat forces.
On 17 January, 1939, Adolph Hitler approved the Z-Plan.  This
plan in addition to building multiple surface ships provided
for the construction of 233 more U-Boats.20 The
construction would not be complete until 1948.  When World
War II broke out, Admiral Doenitz was in command of just 56
U-Boats.21 Throughout the war years German industry would
produce scores of U-Boats.  However, Admiral Doenitz would
never command the size of force he felt necessary to wage a
decisive campaign.
    The foresight of a few key influential individuals
enabled Germany to maintain a U-Boat technology base after
the First World War despite the worlds attempts to eliminate
her warfighting capability.  While the rest of the world
attempted to achieve military parity in efforts to preclude
another major confrontation, Germany gradually rose from her
postwar status as a second class powerless nation to a nation
capable of once again producing the machines of war.  Her
covert operations in U-Boat engineering and production
enabled her to be prepared for production when Adolph Hitler
came to power.  The chain of events which ensued overwhelmed
Admiral Doenitz' U-Boat production projections.  The number
of boats Doenitz had in his command never met the need for
his concept of employment.  Therefore he was never able to
fully implement his plan of action.  One can only guess at
the outcome of World War II had Doenitz had his 300 U-Boats
at the beginning of hostilities.
1.  Richard Garrett, Submarines (Boston: Little, Brown and Co.,
    1977) ,p.61.
2.  Ibid., p.69.
3.  Ibid., p.69
4.  Ibid., p.71
5.  Edwin P. Hoyt, U-Boats (New York: McGraw Hill, 1987),p.2
6.  Eberhard Rossler, The U-Boat, tr. Harold Erenberg (Naval
    Institute Press, 1981),p.88.
7.  Garrett, p.72.
8.  Douglas Botting, The Seafarers: The U-Boats (Alexandria,
    Virginia: Time-Life Books, 1979),p.76.
9.  Garrett, p.72.
10. Wolfgang Frank, The Sea Wolves (London: Weidenfeld and
    Nicolson, 1955) ,p.9.
11. Hoyt, p.4.
12. Frank, p.10.
13. Vice Admiral Sir Arthur Hezlet, The Submarine and Seapower
    (New York: Stein and Day, Publishers, 1967),p.118.
14. David Mason, U-Boat The Secret Menace (New York: Ballantine
    Books, Publisher, 1968),p.10.
15. Hoyt, p.5.
16. Frank, p.13.
17. Hoyt, p.7.
18. Garrett, p.78.
19. Mason, p.13.
20. Rossler, p.11.
21. Hoyt, p.9.
Botting, Douglas.  The Seafarers: The U-Boats. Alexandria,
    Virginia: Time-Life Books, 1979.
Frank, Wolfgang.  The Sea Wolves. London: Weidenfeld and
    Nicolson, 1955.
Garrett, Richard.  Submarines. Boston: Little, Brown, and Co.,
Hezlet, Vice Admiral Sir Arthur.  The Submarine and Sea Power.
    New York: Stein and Day, 1967.
Hoyt, Edwin P.  U-Boats. New York: McGraw Hill, 1987.
Mason, David.  U-Boat The Secret Menace. New York: Ballatine
    Books, 1968.
Rossler, Eberhard.  The U-Boat. Tr. Harold Erenberg. Naval
    Institute Press, 1981.

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